Astragalus L. Sp. PI

Astragalus L. Sp. PI, 755. 1753 & Gen. Pl, Ed. 5, 335. 1754

Type species:— Astragalus alpinus L., Sp. Pl. 2: 760. 1753.

In Mexico, always herbaceous, annual, or perennial, commonly caulescent, rarely acaulescent, occasionally, the stems emerging from a subterranean caudex, rarely rooting at nodes, resembling stolons. Pubescence simple or dolabriform (knife-shaped), trichomes with a central axis and two lateral arms of the equal or different size, almost always one arm longer than the other. Stipules free or adherent to the petiole, clasping or clasping and connate, forming a sheath, commonly ciliate on the margins. Leaves ordinarily imparipinnate, petiolate or subsessile, leaflets commonly in pairs or occasionally subalternate along the rachis; stipels absent. Inflorescences pedunculate, rarely subsessile, arranged in clusters, umbels or axillary head-like; bracts small, membranous; bractlets 0–2, little, membranous or scaly, at the base of the calyx. Flowers papilionate (zygomorphic), commonly small, sometimes large and showy, regularly with graduated petals, very rarely, the keel equal or longer than wings, purple, red, violet, pink, white, yellow, whitish to pale yellow or a combination of two or even three colors on a flower; calyx campanulate, cylindrical, infrequently urceolate, symetrical or asymetrical at base, sometimes breaking on one side as the fruit develops, teeth 5, equal or subequal, triangular to lanceolate; the banner erect, regularly bent back to varying degrees in the distal middle, rounded or retuse at apex, rarely with a small basal claw; the wings regularly oblique-oblong, auriculate and basally clawed; the keel equal or shorter than wings, rarely longer, commonly incurved distally, auriculate and clawed; stamens 10 and diadelphous (9+1); the anthers isomorphic; ovary sessile to stipitate, unilocular, with few to many ovules; style filiform, glabrate, stigma terminal, glabrate. Pod variable in size, shape, texture and dehiscence, sessile or stipitate and attached to the receptacle, or elevated in either a stipe continuous with the pod or in a gynophore (similar to a stipe but articulate and brittle, allowing the fruit be detached from the receptacle at this joint), linear, oblong, elliptical, ovoid, obovate, clavate or bladder-shaped, straight or curved, cylindrical, laterally compressed, dorsoventrally or triquetrically (triangular in cross-section), commonly longitudinally grooved on the back, opaque, semitransaprent or diaphanous, papyraceous, leathery to coriaceous, the dorsal suture intruded, to form an incomplete or complete longitudinal septum, dividing the pod cavity into two chambers; 2-many ovules, dehiscence in situ or after detachment and fall; seeds reniform or mitt-shaped, variables in color and texture.

Currently, in Mexico, there are no Astragalus species in protection status within NOM-096-2010 (2010), However, IUCN Threatened species (2022) register 30 species of Astragalus occurring in North America and Mesoamerica, most of them consider as Least Concern. Seven of these occur also in Mexico: A. didymocarpus H. & A. (1840: 334), A. ervoides H. & A. (1840: 417); A. crotalariae A. Gray (1864: 216); A. lentiginosus Douglas (1931: 151); A. mollissimus Torr. (1827: 179); A. nuttallianus Speg. (1902: 265), and A. waterfallii (Barneby (1953: 31). Of the total of species in Mexico, at least 17 of them have restricted distribution to a state, a municipality, or the type locality. Thirteen of these species are distributed in the northern states, from Baja California Sur to Nuevo León and San Luis Potosí. Thirteen of these species are found in mesic or cold climates, in mountains and portions of the highlands, and the other 14, distribute in low plains from arid, semi-arid, and Medeterranean climates. Among the most endangered species that are most in danger of disappearing because of human impact are A. radicans Hornem (1815: 708) and A. harshbergeri (Rydb.) A.E.Estrada, Villarreal & A.Delgado (470:127–130), since they are distributed in the area of the Valley of Mexico surrounding Mexico City and high mountain areas subject to great anthropogenic pressure in the state of Mexico. The last collections recorded for both species were made in the State of Mexico, 1982, A. radicans (Rzedowski 37875 (ENCB, IEB)) and 1972, A. harshbergeri (Rzedowski 29055 (CAS, ENCB)). Other species that can be considered at least threatened because of their restricted distribution, inhabiting only in one ecosystem, anthropogenic disturbance, human settlement construction and habitat destruction are: A. cenorrhynchus Barneby (1982: 78–80) (Oaxaca) only known from the type locality, A. comonduensis A. E. Estrada, Rebman & Villarreal (2019:59–60) (Baja California Sur), known only from two specimens collected at the edge of the Llano la Laguna. Astragalus guanajuatensis Rzed. & Calderón (2015: 110) (Guanajuato), A. mario-sousae A. E. Estrada, A. Villarreal & C. Yen (2005: 314) (Nuevo León), A. moranii Barneby (1976: 208) (Baja California), A. oxyphysus A. Gray (1864: 218) ((Baja California), A. piscinus M. E. Jones) (1895: 645) (Baja California Sur), A. pilosor R.W. Spellenb. & E.W. Anderson (2019: 131– 140)(Chihuahua), A. pueblae M. E. Jones (1912: 35) (Puebla), A. sagitticarpus A. E. Estrada, Villarreal & Encina (2020: 166–167) (Morelos), A. spellenbergii A. E. Estrada, S. González & Villarreal (2016: 92) (Durango), and A. tioides (Rydb.) Barneby (1964: 171) (San Luis Potosí) are known only from the type locality; A. harbisonii Barneby (1953: 34) has a very restricted range adjacent to coast areas and tourism developments; A. sanctorum Barneby (1976: 275) (Baja California) is only known from the Punta Banda area and threatened with development by Ensenada.

Key to identify the taxa of Astragalus in Mexico.

1. Plants of the peninsula of Baja California (Zone I, Fig. 1)................................................................................................................2

- Plants not from the penínula of Baja California...............................................................................................................................36

2. Flowers red; plants acaulescent....................................................................................................................................... A. coccineus

- Flowers not red; plants caulescent or acaulescent..............................................................................................................................3

3. Pods 5 mm long or shorter, bilocular, 2-ovulate; annual plants.........................................................................................................4

- Pod 5.5 mm long or longer uni or bilocular; ovules 4-many; annual or perennial plants..................................................................5

4. Flowers and fruits erect; petals 4–9.8 mm long; fruit transversally or diagonally sulcate with 4–7 ridges, almost included into the calyx when mature; Baja California and Sonora...................................................................................................... A. didymocarpus

- Flowers and fruits pendulous; petals 2.5–3.3 mm long, very rarely longer; fruit not transversally or diagonally sulcate, half of its length exerted from calyx; only in Baja California.................................................................................................... A. gambelianus

5. Petals large, banner 21–28 mm long; petals of the wings 19.5–25 mm long; keel petals 17.3–21 mm long; in Mexico, recorded only around Mexicali (Baja California)................................................................................................................................. A. crotalariae

- Petals, all shorter; plants around Mexicali and other areas of Baja California and Baja California Sur...........................................6

6. Pod triquetrous, linear-elliptic to oblong-elliptic but laterally compressed, never ellipsoid-flared or inflated, resembling a bladder............................................................................................................................................................................................................7

- Pod widened or inflated resembling a bladder or the pod faces inflated only in the area where seeds are located.........................12

7. Pod oblong to elliptic, laterally compressed, unilocular, narrowed at both ends, basally ending in a stipe......................... A. filipes

- Pod triquetrous, laterally compressed, but bilocular or almost so, basally wide and sessile or ending in a stipe..............................8

8. Leaflets 23–33 per leaf; flowers 20–25 per raceme; calyx 6.1–8.1 mm long; wings 7.2–10.2 mm long....................................................................................................................................................................................................... A. brauntonii var. lativexillum

- Leaflets 5–15 per leaf; flowers 1–10 per raceme; calyx 2.6–5.6 mm long; wings 3.3–6 mm long...................................................9

9. Keel petals tip acute beaked; pod apparently sessile, but elevated on a minute, articulated gynophore 0.3–0.8 mm long, thus soon falling from receptacle; only in Baja California.......................................................................................................... A. acutirostris

- Keel petals tip commonly rounded; pod sessile or stipitate, if stipitate, elevated in a stipe continuous with the pod, thence it strongly attached to the receptacle and persistent for a time; Baja California and Baja California Sur..........................................10

10. Pod stipitate, curved or sigmoid; plant perennial; leaves up to 18 cm long, the leaflets gradually decreasing in size towards the apex, the pairs separated by 2–3 times the width of each other................................................................................... A. orcuttianus

- Pod sessile, straight or curved; plant annual or biennial; leaves up to 8.5 cm long, the leaflets commonly the same size, and not widely separated...............................................................................................................................................................................11

11. Pod straight or almost so; banner 8.1–10 mm long; wings 8–9.3 mm long; endemic to Sierra La Laguna, Baja California Sur...................................................................................................................................................................................... A. francisquitensis

- Pod curved; banner 4–7.5 mm long; wings 3.7–6.2 mm long; Baja California and Baja California Sur................... A. nuttallianus

12. Pod elevated from the receptacle by a 0.4 mm long, but commonly 0.7 mm or longer stipe or gynophore....................................13

- Pod sessile in the receptacle, or, if elevated (rarely) from receptacle, not more than 0.4 mm.........................................................18

13. Pod elevated from receptacle by a true stipe, the stipe continuous with the receptacle, thence, the pod firmly attached to the receptacle; petals white, cream, ochroleucous, or rarely pink-purple veined..................................................................................14

- Pod elevated from receptacle by a gynophore articulated (joined), not continuous with the receptacle, thence, the pod not firmly attached to the receptacle, soon caducous; petals white, cream, green-white, pink or purple.........................................................15

14. Stipe always strigulose, pod subglabrate to strigulose, inflated, never strongly flattened; along the entire western coast, from Rosarito to Santa Rosaliíta, also on the Coronados, Todos Santos in the Pacific Ocean and Smith´s Island...................................................................................................................................................................................................... A. trichopodus var. lonchus

- Stipe and pod glabrous, inflated resembling a bladder, but strongly compressed laterally, two-sided, its faces inflated only in the area where seeds are located; around Gustavo Diaz Ordaz, San Telmo, Potrero, Meling Ranch, El Jonuco, San Rafael and Mina Santa Cruz to El Canuto............................................................................................................................................ A. oxyphysopsis

15. Pod elevated in a very small, 0.4–0.7 mm long gynophore, non-exserted from calyx; petals rose-purple.................... A. proriferus

- Pod elevated in a longer, 3–11 mm long gynophore, exserted from calyx; petals white immaculate, green-whitish, cream, blueviolet, purple, rose purple to blue when drying...............................................................................................................................16

16. Calyx 3.1–4.8 mm long; banner 8.3–9 mm long; petals of the wings 7.4–8.3 mm long, keel petals 7–8.2 mm long; petals purple, blue-violet, becoming blue when drying; gynophore 3–4 mm long, strigulose; endemic to the Sierra de Juárez, Baja California................................................................................................................................................................................................ A. moranii

- Calyx 5.5–10.3 mm long; banner 13–19 mm long; petals of wings 12.3–18 mm long; keel petals 10–14.7 mm long; gynophore (3–) 8.5–11 mm long; Baja California and Baja California Sur........................................................................................................17

17. Flowers 20–67 per raceme, white or cream, immaculate; calyx 8.5–10.3 mm long; keel petals 13–15 mm long; ovules 10–18............................................................................................................................................................................................... A. oxyphysus

- Flowers 7–18 per raceme, purple, pink-purple, green-white or cream and turning yellowish when drying; calyx 5.5–8.2 mm long; keel petals 10–11.2 mm long; ovules 20–27..................................................................................................................... A. fastidius

18. Stipules both, clasping and connate, surrounding the total stem´s circumference and forming a sheath around it.........................19

- Stipules free, clasping or decurrent, not connate.............................................................................................................................21

19. Plant small, the stems up to 11 cm long; peduncles 0.5–1.5 cm long; petals small, banner 7.3–10 mm long, wings 7–9.3 mm long, keel 6.9–8.8 mm long; mountains of Sierra de Juarez and Sierra de San Pedro Mártir; conifer forest, 1700–2475 m............................................................................................................................................................................................................ A. circumdatus

- Plants larger, the stems 30–70 cm long; peduncles 2.5–10 cm long; petals larger; coastal dunes...................................................20

20. Pod relatively small, 1.5–2 cm long, minute strigose; leaflets 13–23; peduncles 2.5–10 cm long; ovules 22–27; west coast in central Baja California, from Nueva Odisea, El Socorrito, Valle Tranquilo to Punta Baja........................................................ A. harbisonii

- Pod large, 2.7–4 cm long, minutely tomentose, the trichomes extremely fine and curly; leaflets 15–37; peduncles 8–16 cm long; ovules 32–40 from north of Camalú, Colonia Vicente Guerrero, Los Molinos, Campo San Ramón, Cabo San Quintín, Santa María to El Socorrito, El Socorro and Campo Costa Rica.................................................................................................... A. anemophilus

21. Pod widened, but not inflated resembling a bladder, stiff, 3–3.8 times longer than wide; far north of Baja California..................22

- Pod inflated resembling a bladder, papyraceous, 2–2.5 times longer than wide..............................................................................23

22. Pod bilocular, the septum complete; keel (9.5–) 11.5–16.3 mm long, its blade 7–10 mm long...... A. lentiginosus var. borreganus

- Pod unilocular, septum absent; keel 9.4–9.8 mm long, its blade 4.6–5 mm long; known only fot he type locality (Tijuana City............................................................................................................................................................................................. A. tijuanensis

23. Racemes commonly with 10 flowers or fewer (rarely few more)....................................................................................................24

- Racemes 10 flowers or more............................................................................................................................................................27

24. Petals ochroleucous pale rose, white or purple-lavender turning bluish with age, the banner 3.3–6.5 mm long; annual; ovules 3–9; pod erect...........................................................................................................................................................................................25

- Petals white, purple to ochroleucous and lavender-veined, longer, the banner up to 7.2 mm long; annual, biennial or perennial; ovules 12–19; pod extended or pendulous.......................................................................................................................................26

25. Herbage densely white silky-canescent; leaflets not mucronate, equally pubescent in both adaxial and abaxial leaf surfaces; calyx 3.2–4.4 × 1.5–2.4 mm; ovules 3–7; pod scarcely inflated, not evidently bladdery, but laterally compressed at both ends and strongly so at the apex, the valves papery, opaque, densely white canescent to strigulose-pilose; extreme northeastern Baja California and northwestern Sonora.............................................................................................................................................................. A. aridus

- Herbage green-strigulose, not densely pubescent; leaflets mucronate and glabrate adaxially, not equally pubescent on both leaf surfaces; calyx 2–2.8 × 1–1.2 mm; ovules 7–9; pod inflated, bladdery, not laterally compressed, shiny, sub-diaphanous, minutelystrigulose; Baja California Sur, near Comondú (26°06’N, 111°46’W)................................................................... A. comonduensis

26. Pod trichomes appressed and straight, the valves thin-papery and sub-diaphanous red to purple tinted; leaflets acute at both ends............................................................................................................................................................................................ A. insularis

- Pod trichomes somewhat curly, the valves firm, opaque, no trasluscent, sometimes with purple or dark-reddish tints; leaflets rounded to obtuse apically............................................................................................................................................. A. sabulonum

27. Flowers and pods aggregated forming a compact globose, subglobose to oblong head; adjacent to coastal dunes, inhabiting in cemented terraces..................................................................................................................................... A. hornii var. minutiflorus

- Flowers and pods loosely racemose; coastal dunes, terraces, deserts and mountains......................................................................28

28. Plants densely silver-pubescent to leaden-pubescent, exclusive from sandy coastal dunes....................................... A. magdalenae

- Plants green of different tone to cinerous, neither silver nor leaden-pubescent, or if so, not from coastal dunes...........................29

29. Flowers white, ochroleucous, green-white or yellowish..................................................................................................................30

- Flowers purple, rose-purple, sometimes rose brilliant.....................................................................................................................32

30. Wings 8–10.7 mm long; keel claw 2.3–4.4 mm long....................................................................................................... A. douglasii

- Wings 11–15 mm long; keel claw 5.1–6 mm long...........................................................................................................................31

31. Foliage dense, the leaflets close to each other; banner 11–15.3 mm long; wings 10.6–15 mm long, almost the same length of the banner: leaflets 25–41, the longest averaging 15–37 mm long................................................................................... A. pomonensis

- Foliage lax; the leaflets separated to each other; banner 14.4–17.8 mm long, evidently longer than the wings; wings 12.3–14.2 mm long; leaflets 17–31, the longest averaging 11–17 mm long........................................................................................ A. sanctorum

32. Flowers relatively short; wings 5.5–8 mm long, the claw 2.2–2.8 mm long, the blade 3.8–5.7 mm long; keel 5.7–7.6 mm long, the claw 2.2–3.4 mm long, the blade 3.8–4.8 mm long; ovules 12–16..................................................................................................33

- Flowers larger; wings (7)8.5–11.6, the claw (2.8) 3–4.9 mm long, the blade (4.5) 5.6–7.5 mm long; keel (6.3) 7.7–9.2 mm long, the claw (2.5) 3.7–4.8 mm long, the blade (4) 5.1–5.5 mm long; ovules (7)24–31.................................................................................34

33. Stems, leaves and pods with dense villous to hirsute pubescence, the trichomes spreading or somewhat incurved; the pod not subdiaphanous...................................................................................................................................................................... A. proriferus

- At least stems and leaves with strigulose pubescence, the trichomes appressed to subappressed; pod sparsely strigulose; the pod sub-diaphanous.............................................................................................................................................................. A. idrietorum

34. Pod firmly attached to the receptacle, falling together with pedicel; flowers purple; plants on coniferous forest of San Pedro Mártir National Park...................................................................................................................................................................... A. gruinus

- Pod soon caducous, not strongly attached to the receptacle; flowers purple, pink to pink-brilliant; plants on conifer forest and adjacent scrublands or in dune areas of low plains at the Pacific Ocean.........................................................................................35

35. Pod 5–15 mm long; fertile pedicels persistent; leaflets 11–21; petals purple to pink or rose-brilliant; banner 7–10.4 mm long; wings 6.3–9.4 mm long, its claw 2.4–3.8 mm long; conifer forest and adjacent scrublands in sierras de Juárez and San Pedro Mártir; Baja California............................................................................................................................................................................ A. palmeri

- Pod 20–30 mm long; fertile pedicels caducous; leaflets 15–25; petals purple; banner 10–13 mm long; wings 9.2–11.5 mm long, its claw 4–4.9 mm long; low plains at the Pacific Ocean, in extreme southwestern Baja California to the west of Jesús María....................................................................................................................................................................................................... A. piscinus

36. Plants of Sonora, Chihuahua, Coahuila, Nuevo León, Tamaulipas, Sinaloa, Durango, Zacatecas, Aguacalientes, and San Luis Potosí (Zone II, Fig. 1).....................................................................................................................................................................37

- Plants of Nayarit, Jalisco, Guanajuato, Querétaro, Hidalgo, Morelos, Puebla, Veracruz, Colima, Michoacán, State of Mexico, Mexico City, Guerrero, Oaxaca, and Chiapas (Zone III, Fig. 1)....................................................................................................108

37. Pubescence dolabriform, the trichomes joined at a point before the end, in the form of “v” or “t”, with equal or unequal ends.................................................................................................................................................................................................................38

- Pubescence basifixed with simple trichomes...................................................................................................................................42

38. Petals ochroleucous, greenish-white or lavander or, at least the veins with lavender tones, sometimes dyed purple or blue-purple at the apex or the edges; stems 12 cm long or shorter; calyx teeth up to 5.2 mm long; in Mexico recorded only in Coahuila......................................................................................................................................................................................................... A. lotiflorus

- Petals green-whitish, pink-whitish, magenta, purple-magenta, purple or pink; stems 15 cm long or longer; calyx teeth up to 4.5 mm largo; Coahuila and other states........................................................................................................................................................39

39. Leaves 7.5 cm long or shorter; peduncles 2–10.5 cm long; keel 10 mm long or shorter; calyx tube (3.1–) 4.1–10.5 mm long......40

- Leaves up to 13 cm long; peduncles (2.5) 10–20 cm long; keel (8.2) 10–19.6 mm long; calyx tube (2.2) 3–3.8 mm long..............41

40. Pod deflexed, bilocular; 7–12.5 mm long, triquetrous, oblong to narrow-oblong; calyx 3.1–5.2 mm long, the teeth up to 2.6 mm largo; banner 6–8.2 × 3–4.3 mm; keel 4.5–6.6 mm long; wide distribution, but not in Chihuahua and Sonora......... A. hypoleucus

- Pod ascendant, unilocular, (10–) 13–22 mm long, inflated resembling a bladder, oblong-elliptic; calyx (4.5) 5.8–8 mm long, the teeth 2–4.5 mm long; banner 8.3–11.8 × 6–9 mm; keel 7.3–10 mm long; Chihuahua and Sonora............................ A. humistratus

41. Flowers relatively small; calyx 4.5–7 mm long; banner 8–12 mm long, wings 6.7–10 mm long, keel petals 8–10.4 mm long; leaflets (5–)9–17; pod triquetrous, straight, semi-straight, rarely slightly curved, linear to linear-oblong, 4 mm wide or narrower, bilocular, no humistrate; stipules free; Sonora............................................................................................................... A. arizonicus

- Flowers larger; calyx 9.3–14.2 mm long; banner 16.2–24.5 mm long, wings 15.1–22.4 mm long, keel petals 13.2–19.6 mm long; leaflets (7–)11–21; pod somewhat triquetrous but semi-lunate, 5–10 mm wide, unilocular, humistrate; stipules semi to completely clasping; Chihuahua...................................................................................................................................................... A. amphioxys

42. Petals all red; banner 22–32 mm long; wings 18–31 mm long; keel petals 18–27 mm long; Coahuila and Nuevo León....................................................................................................................................................................................................... A. sanguineus

- Petals of another color, or if red, combined with another color; banner smaller than 21 mm long, wings and keel smaller than 17 mm long............................................................................................................................................................................................43

43. Calyx 2.8–3 cm long; petals yellow; endemic of Chihuahua.......................................................................................... A. hartmanii

- Calyx 1.5 cm long or shorter; petals yellow or different colors; Chihuahua and other states..........................................................44

44. Pod strongly dorso-ventrally flattened, in a wide “u” shaped or car winshield shaped, curved as seen of profile, frequently wider than longer, sessile or elevated in a gynophore, in north of Mexico, locally distributed in far north of Tamaulipas (Matamoros), north-central Coahuila and south-western San Luis Potosí..............................................................................................................45

- Pod not strongly dorso-ventrally flattened, commonly longer than wider, or if wider than longer, then inflated or widened, sessile or stipitate; Tamaulipas, San Luis Potosí, and other states...............................................................................................................46

45. Leaflets 11–13 per leaf; pod elevated in a gynophore 1.5–2.3 mm long; Coahuila and Tamaulipas............................. A. brazoensis

- Leaflets 15–23 per leaf; pod sessile; San Luis Potosí..................................................................................................... A. scutaneus

46. Pod 4 mm long or shorter, bilocular, bi-ovulate, when ripe, it separates into two indehiscent sacs containing one seed each; annual weak plants; northern end of Sonora............................................................................................... A. didymocarpus var. dispermus

- Pod 4 mm or longer, uni to bilocular, ovules 3 or more, if pod 2-ovulate, it entirely dehiscent; plants perennial; Sonora and other states.................................................................................................................................................................................................47

47. Bracts cymbiform (boat shaped); pod triquetrous, sessile, 7–12 mm long; leaves 3–7.5 cm long; leaflets 2–10 mm long; peduncles 4–10 cm long; calyx 2.7–3.6 mm long; banner 5.6–6.5 mm long; Chihuahua and Durango.............................................. A. daleae

- Bracts flattened, never cymbiform; pod triquetrous, inflated resembling a bladder or of different shape, sessile to stipitate; leaves, peduncles and flowers with varied sizes..........................................................................................................................................48

48. Pubescence of stems, petioles and peduncles dense, hispid to pilose, the trichomes straight extended or retrorse; Coahuila, Nuevo León and Durango............................................................................................................................................................................49

- Pubescence of stems, petioles and peduncles with trichomes appressed and ascendant, never straight extended or retrorse.........52

49. Pod oblong to narrow-oblong, exserted from calyx; calyx campanulate, 4.3–6.7 mm long; banner 6.5–10.2 mm long; wings 5.2–9.2 mm long; keel 4–7.2 mm long; ovule 6–18; Durango, Coahuila, Nuevo León and San Luis Potosí.................................50

- Pod wide-oblong, inflated, immersed in the calyx; calyx urceolate-globose to urceolate-suboblong, 8–10 mm long; banner 13.8–16 mm long; wings 11.8–13 mm long; keel 9–11 mm long; ovules 4; Coahuila and Nuevo León......................................................51

50. Petals purple, light-purple but turning ochroleuocus quickly and remaining so when dry; pod sessile or stipitate, stipe 0.2–3 mm long; stems up to 65 cm long; calyx 5–6.7 mm long; banner 7.2–10.2 × 5.3–7.7 mm; wings 7.2–9.2 mm long; keel 6–7.2 mm long; pod 10–18 mm long; ovules 9–18; Coahuila, Nuevo León and San Luis Potosí................................................................ A. greggii

- Petals yellow; pod short stipitate, stipe 0.2–0.3 mm long; stems up to 15 cm; calyx 4.3–4.7 mm long; banner 6.5–7.2 × 2.8–3 mm; wings 5.2–5.3 mm long; keel 4–4.2 mm long; pod 7–8 mm long; ovules 6–7; endemic of Durango....................... A. spellenbergii

51 Peduncles shorter than leaves; racemes congested, 2–5 cm long; calyx urceolate-globose, with white trichomes only; Coahuila and Nuevo León............................................................................................................................................................... A. pomphocalyx

- Peduncles as long as or longer than leaves; racemes loose, 3–10 cm long; calyx urceolate-suboblong, with black and white trichomes mixed; endemic of Coahuila............................................................................................................................... A. rupertii

52. Keel of the same size or little longer than petals of the wings; Sonora, Chihuahua and Sinaloa....................................... A. gentryi

- Keel shorter than petals of the wings; Sonora, Chihuahua, Sinaloa and other states.......................................................................53

53. Petals pink, purple, lavander, lilac, cherry, violet, purple-reddish, bicolored (even in its venation or some part of the petals) or white, but mixed with other color, but never green-withish o green-yellowish...............................................................................54

- Petals all white, cream, yellow, pale-yellow, ochroleucous, concolorous, if bioclored, these green-whitish or green-yellowish...96

54. Pod triquetrous (rarely laterally compressed in A. nothoxys) to trigonous, triangular in cross section, flattened or somewhat widened or inflated, but triquetrous................................................................................................................................................................55

- Pod flattened dorso-ventrally, linear-oblong, oblong-elliptic, obovate, oblong-ellipsoid, clavate-oblong, lanceolate-elliptic, widened, wide-cylindric to inflate resembling a bladder, never triquetrous....................................................................................76

55. Plants acaulescent, the longest leaves commonly larger than stems; rare in Mexico, recorded only in north end of Chihuahua and Coahuila.......................................................................................................................................................................... A. waterfallii

- Plants caulescent, the stems always longer than leaves; Chihuahua, Coahuila and other states......................................................56

56. Pod stipitate, stipe 0.4–7 mm long...................................................................................................................................................57

- Pod sessile, never stipitate................................................................................................................................................................62

57. Laeflets 10–37 mm long; calyx 7.3–10.5 mm long, its tube 4.7–9 mm long; banner 15.4–19 mm long; wings 12.4–19 mm long; keel 10.6–15.4 mm long; stipe 3.5–7.4 mm long; grasslands and gypsic soils; San Luis Potosí and Nuevo León.......................................................................................................................................................................................... A. racemosus var. racemosus

- Leaflets 2–13 mm long; calyx 2.2–7.2 mm long, its tube 1.6–3.2 mm long; banner 4.9–10.2 mm long; wings 4.4–10 mm long; keel 3.9–7.6 mm long; stipe 0.1–2.7 mm long; mountains of Sinaloa, Chihuahua, Coahuila, Durango and San Luis Potosí................58

58. Calyx 2.2–2.9 mm long; pod 4–8 mm long; endemic of Chihuahua................................................................................. A. scalaris

- Calyx 3.4–7.2 mm long (very rarely 2.9 mm long in San Luis Potosí, but, the pod longer than 8 mm long); pod 8.5–22 mm long; Sinaloa, Chihuahua, Coahuila, Durango and San Luis Potosí.........................................................................................................59

59. Banner 2.2–2.5 mm wide; endemic from mountains of southwestern Chihuahua.............................................................. A. pilosior

- Banner 3–6 mm wide; plants from Sinaloa, Chihuahua, Coahuila, Durango and San Luis Potosí.................................................60

60. Banner 4.5–7 mm long; wings 6–7.9 mm long; stipe 0.1–0.5 mm long; pod 8.5–13 mm long; San Luis Potosí............................................................................................................................................................................................ A.micranthus var. micranthus

- Banner 6.3–10.2 mm long; wings 6.6–10 mm long; stipe 0.4–2.7 mm long; pod (11–) 14–22 mm long; Coahuila, Chihuahua, Durango and Sinaloa........................................................................................................................................................................61

61. Flowers pink-purple, pink-purple to reddish-violet; stipe 1–2.7 mm long; endemic of Coahuila.................................... A. carminis

- Flowers white, whitish, the keel petals purple or pinkish; stipe 0.4–1.5 mm long; Chihuahua, Durango and Sinaloa.... A. ervoides

62. Racemes 1–7 flowers (rarely up to 12 in A. parvus)........................................................................................................................63

- Racemes with 8-many flowers, or if only 5 flowers, then the racemes 4.5–10 cm long..................................................................65

63. Plants annual, 25 cm or longer, not tufted nor compact radial growth; pod triquetrous, 2–3.6 mm wide; banner 4–6.7 mm long.......................................................................................................................................................................................... A. nuttallianus

- Plants perennial, 20 cm long shorter, tufted or with compact radial growth; pod triquetrous; banner 7.4–9 mm long, if it shorter, then the pod trigonous (tiquetrous but inflated) and commonly wider, up to 4.5 mm.....................................................................64

64. Banner 7.3–9 mm long; pod triquetrous, 8–19 × 2–3.6 mm, linear to liner-oblong, aereal, never humistrate; calyx 4–5.1 mm long ovules (12–)14–26; Durango, Nuevo León, Cacatecas, San Luis Potosí and Tamaulipas................................................... A. parvus

- Banner 4.4–5.4 mm long; pod trigonous (triquetrous but inflated), 6–11 × 3–4.5 mm, humistrate; calyx 2.6–3.6 mm long; ovules 2–17; Chihuahua, Coahuila, Durango, and Zacatecas.............................................................................................. A. quinqueflorus

65. Stipules all connate, and constituing a sheath around to the stem´s circumference, the upper ones joined at the base or up to half of its length; Durango, San Lus Potosí and Zacatecas....................................................................................................... A. esperanzae

- Stipules free or clasping, or if connate (basal ones), then the pod caducous and 5–15 x 2–3.5 mm, or if almost 3.8 mm wide, not longer than 11 mm............................................................................................................................................................................66

66. Calyx small, 2.4–3.6 mm long..........................................................................................................................................................67

- Calyx longer, 3.8–8.5 mm long, rarely shorter.................................................................................................................................68

67. Peduncles 1.5–4.5 cm long, racemes 0.5–1.6 cm long; flowers 7–22 per raceme; Coahuila, Nuevo León and Zacatecas, 2500–3650 m......................................................................................................................................................................................... A. purpusi

- Peduncles (3–) 6–12 cm long; racemes 3–18 cm long; flowers (10) 25–65 per raceme; Chihuahua to San Luis Potosí, at different elevations..........................................................................................................................................................................................69

68. Pod semi-ovate, 3.1–7.8 × 2–2.7 mm; racemes up to 18 cm long; leaflets up to 10.3 mm long; Aguascalientes, Chihuahua, Durango, Nuevo León and Zacatecas............................................................................................................................................. A. goldmanii

- Pod linear-elliptic to lanceolate, 6–12 × 1.3–2 mm; racemes up to 8 cm long; leaflets up to 24 mm long; Chihuahua, Coahuila, Durango, Sinaloa and San Luis Potosí............................................................................................................................ A. vaccarum

69. Ovules 6–8; racemes 0.5–2.5 cm long; endemic of Sonora........................................................................................... A. hypoxylus

- Ovules (8–)11–26; racemes longer or if up to 2–2.5 cm long, then with more than 8 ovules; Sonora and other states..................70

70. Banner 3.4–4.3 mm wide; keel claw 4.7–5.8 mm long; stems 22 cm long or shorter; leaflets 1–6.2 mm long; Chihuahua and Durango.............................................................................................................................................................................. A. pringlei

- Banner (4–) 5–9 mm wide; keel claw 1.9–4.4 mm long; stems 25 cm or longer; leaflets (5–) 7–21 mm long; Chihuahua, Durango and other states.................................................................................................................................................................................71

71. Racemes completely developed 0.2–2 cm long; mature pod 10–12 mm long; local species in Nuevo León and the border from Chihuahua and Sonora......................................................................................................................................................................72

- Racemes completely developed longer, 2.5–10 cm; mature pod 13–22 mm long, or if the racemes as short as 2 cm long, then, the mature pods longer than 12 mm long; species with wider distribution............................................................................................73

72. Calyx teeth 1–1.5 mm long; endemic form Nuevo León.......................................................................................... A. mario-sousae

- Calyx teeth 1.6–2.3 mm long; endemic of the mountains at the Sonora-Chihuahua border.............................................. A. martinii

73. Calyx 3.2–4.8 mm long, the teeth 1–1.4 mm long; racemes up to 14 cm largo; flowers (15–)25–55 per raceme; keel 5.4–6.3 mm long; Sonora, Chihuahua, Coahuila, Durango, San Luis Potosí and Zacatecas.............................................................. A. hartwegii

- Calyx (4.8–) 6–7 mm long, its teeth (1–4–) 2.5–3 mm long; racemes up to 10 cm long; flowers 1–15, or if up to 25, then the keel 6.5–8.4 mm long...............................................................................................................................................................................74

74. Keel claw 1.8–3 mm long; keel 4.5–6.6 mm long; trichomes of stems and foliage up to 1 mm long; Chihuahua, Coahuila and Nuevo León................................................................................................................................................................... A. emoryanus

- Keel claw (3.1–) 3.3–4.8 mm long; keel (6.5–) 6.7–9 mm long; trichomes on stems and leaves up to 0.5 mm long; Chihuahua, Coahuila, Nuevo León, Durango, Sonora and Zacatecas.................................................................................................................75

75. Calyx tube 3.2–3.8 mm long; banner up to 12 mm long; pod 10–16 mm long; Chihuahua and Sonora.......................... A. nothoxys

- Calyx tube (3.6–) 4–4.9 mm long; banner 10–15 mm long; pod (13–) 15–22 mm long; Coahuila, Nuevo León, Durango and Zacatecas......................................................................................................................................................................... A. coahuilae

76. Pod stipitate......................................................................................................................................................................................77

- Pod sessile........................................................................................................................................................................................83

77. Calyx 3.1–4.6 mm long; banner 5.5–7.4 mm long; wings 5–6.5 mm long; stipe tiny, 0.1 mm long, the pod almost sessile; Sonora and Peninsula of Baja California....................................................................................................................................... A. insularis

- Calyx 5–8.7 mm long, sometimes less than 5 mm (4.1 mm long), if so, not in Sonora; banner (7.4–) 8–17 mm long; wings 7.1–16.1 mm long; stipe 1 mm or longer; Sonora, Baja California and other states......................................................................................78

78. Flowers 2–5 per raceme; endemic of San Luis Potosí......................................................................................................... A. tioides

- Flowers 7(rarely 5 in A. coriaceus)-50 per raceme; San Luis Potosí and other states.....................................................................79

79. Banner 7.4–9.3 mm long; wings 5.8–6.3 mm long..........................................................................................................................80

- Banner 10–19 mm long; wings 8.5–13.3 mm long..........................................................................................................................81

80. Leaflets (15–)25–47 per leaf; stipules 1–2.5 mm long; endemic of Durango............................................................ A. pennellianus

- Leaflets 11–23 per leaf; stipules (1.5–) 2.8–6 mm long; Durango and San Luis Potosí.................................................. A. potosinus

81. Stipe 5–17 mm long; pod inflate resembling a bladder; flowers green-white, cream-yellowish or white, with purple veins; Sonora..................................................................................................................................................................................... A. trichopodus

- Stipe (0.1–) 1–4 mm long; flowers purple, violet or pink-purple; not from Sonora.........................................................................82

82. Stipe 0.1–1 mm long; racemes 15–80 mm long; wings 12–15.3 mm long; keel 10–13 mm long; pod erect, 12–24 mm long, ovateelliptic; Chihuahua, Coahuila, Nuevo León, Tamaulipas, Durango, San Luis Potosí and Zacatecas............................. A. coriaceus

- Stipe 2–4 mm long; racemes 1.5–10 mm long; wings 9–12.2 mm long; keel 7.3–8.5 mm long; pod deflexed, 13–15 mm long, oblong-elliptic to clavate-oblong; Coahuila and Nuevo León...................................................................................... A. legionensis

83. Pod didymous, subglobose, retuse at both ends; Durango, Nuevo León, San Luis Potosí and Zacatecas....................... A. diphacus

- Pod oblong-elliptic, clavate-ellipsoid, oblique lanceolate-elliptic, ovoid-ellipsoid, obovoid-ellipsoid, oblique-ovoid, ovoid-oblong, ovoid-elliptic, barely inflate resembling a bladder, but always with stiffy or leathery valves or the pod inflate resembling a bladder, never retuse at both ends; in the previously mentioned and other states..........................................................................................84

84. Plants acaulescent or the stems shorter than the largest leaves; pubescence 0.4–0.7 mm largo, the trichomes not spirally twisted; Sonora.............................................................................................................................................................................. A. tephrodes

- Plants caulescent, the stems always longer than longest leaves, or if the stems shorter than leaves and inflorescences, the pubescence pilose and tomentose, with two types of trichomes, short, curly, entangled, and others longer spreading, ascending or forwardly appressed, straight to sinouous, but spirally twisted, 1–2 mm long; Sonora and other states..........................................................85

85. Plants densely pilose and tomentose, with two types of trichomes, short, curly, entangled, and others longer spreading, ascending or rarely appressed, straight to sinuous, but spirally twisted, 1–2 mm long....................................................................................86

- Plants variably pubescent, the trichomes shorter, or if the pubescence of two types (short and long), the trichomes never spirally twisted...............................................................................................................................................................................................87

86. Stems erect and caulescent; peduncles erect when young and in maturity; flowers early deflexed in anthesis; pod persistent on pedicel and dehiscing in the racemes; Chihuahua and Sonora.................................................................................... A. longissimus

- Stems prostrate or decumbent, generally shorter than leaves and inflorescences; peduncles erect when young, humistrate in fruit; flowers ascending in anthesis; pods humistrate, soon caducous when maturing........................................................ A. mollissimus

87. Keel 10–16.2 mm long.....................................................................................................................................................................88

- Keel 3.6–9.7 mm long......................................................................................................................................................................89

88. Peduncles up to 15 cm long; pod unilocular; ovules 20–31; basal stipules connate; Chihuahua, Coahuila, Tamaulipas, Durango, San Luis Potosí and Zacatecas........................................................................................................................................ A. coriaceus

- Peduncles up to 10 cm long; pod bilocular; ovules 10–23; basal stipules clasping and decurrent, not connate; Chihuahua and Sonora.......................................................................................................................................................................... A. lentiginosus

89. Flowers 2–9 per raceme....................................................................................................................................................................90

- Flores 10-many per raceme.............................................................................................................................................................92

90. Calyx teeth 0.8–1.6 mm long; ovules 3–9; Sonora.............................................................................................................. A. aridus

- Calyx teeth (1.7–) 2–3.5 mm long; ovules 10–21; Sonora, San Luis Potosí and Zacatecas.............................................................91

91. Pod somewhat widened but no inflated resembling a bladder, incurved, lunate, ending in an evident beak, its valves fleshy or leathery; racemes 5–25 mm long; Sonora...................................................................................................................... A sabulonum

- Pod inflated resembling a bladder, almost spherical, ending in an obsolete beak or almost absent, its valves papery; racemes 5–53 mm long; San Luis Potosí and Zacatecas............................................................................................ A. wootonii var. candollianus

92. Pod oblong, elliptic to clavate-ellipsoid, never inflated like a bladder, 3.5–6 mm wide; Sonora............ A. cobrensis var. maguirei

- Pod inflated resembling a bladder, Sonora and other states.............................................................................................................93

93. Banner 4.6–7.5 mm long; wings 4.1–7.6 mm long; keel 4.1–6.5 mm long; Sonora, Chihuahua, Durango, San Luis Potosí and Zacatecas..........................................................................................................................................................................................94

- Banner (7.2–) 9.4–12.5 mm long; wings (6.6–) 8–13.3 mm long; keel (6.2–) 7.4–9.5 mm long; Sonora and Chihuahua.................95

94. Flowers (7–)25–32 per raceme; pod 6–13 × 6–10 mm; ovules 8–11; north end of Chihuahua and Sonora..................... A. thurberi

- Flowers (3–)5–15 per raceme; pod (10–)15–37 × (10–) 12–20 mm; ovules (10–)13–21; Sonora, Chihuahua, Durango, San Luis Potosí and Zacatecas.......................................................................................................................................................... A. wootonii

95. Racemes (1.5–) 3.5–12 cm long; banner 7.2–9.4 mm long; wings 6–8.3 mm largo, its blade 4.7–5.7 mm long; keel 6.2–7.5 mm long, its blade 3.8–4.5 mm long; pod (10–) 16–20 mm wide; scrublands, grasslands, unknown of coastal sand dunes; Chihuahua and Sonora..................................................................................................................................................................... A. allochrous

- Racemes 2.5–6.5 cm long; banner 9.4–14.2 mm long; wings (8–) 8.3–13.4 mm long, its blade (5–) 6.8–10.1 mm long; keel (7.4–) 8.2–10 mm largo, its blade 4.7–6.7 mm long; pod 6–11 mm wide; coastal dunes and inland dunes in the del Desierto de Altar; northwestern Sonora.................................................................................................................................................... A. magdalenae

96. Pod triquetrous or trigonous, triangular in cross section, flattened or somewhat widened or inflated, but triquetrous...................97

- Pod oblong-ellipsoid, clavate-oblong, lanceolate-elliptic, widened, wide-cylindric or inflated resembling a bladder, or peltate, never triquetrous.............................................................................................................................................................................104

97. Pod stipitate......................................................................................................................................................................................98

- Pod sessile......................................................................................................................................................................................102

98. Calyx 7.3–10.5 mm long, its tube 4.7–9 mm long; banner 15.4–19 mm long; wings 12.4–19 mm long; keel 10.6–15.4 mm long; locally distributed in three isolated areas of Nuevo León, Zacatecas and San Luis Potosi................ A. racemosus var. racemosus

- Calyx 2.6–7.2 mm long, its tube 2.1–3.8 mm long; banner 5.3–11 mm long; wings 4.9–10.5 mm long; keel 4.4–8 mm long; Sonora, Chihuahua, Durango, Sinaloa and Nuevo León...............................................................................................................................99

99. Leaflets 23–45; peduncles commonly 9.5–22 cm long, rarely shorter; flowers (13–)45–75 per raceme; stipe 3–5.5 mm long; Chihuahua and Sonora................................................................................................................................................. A. longissimus

- Leaflets 9–25; peduncles 2–9 cm long; flowers 5–40 per raceme; stipe 0.4–2 mm long; Sonora, Chihuahua, Durango, Sinaloa and Nuevo León....................................................................................................................................................................................100

100. Stems erect, 40–130 cm tall; keel blade 4.4–4.9 mm long; stipe 1.5–2 mm long; Nuevo León............................ A. regiomontanus

- Stems prostrate, decumbent or incurved-ascendent distally, 20–60 cm long; keel blade 3.1–4.2 mm long; stipe 0.4–2 mm long; Durango, Sinaloa and Chihuahua...................................................................................................................................................101

101. Banner 5.1–5.3 × 3.3 mm; wings 4.9–5.2 mm largo; keel 5.1–5.3 mm long; stipe 0.5–0.9 mm long; pod 2.2–2.5 mm wide; Sonora, Sinaloa and Durango......................................................................................................................................................... A. sinaloae

- Banner 6.2–10.2 × 3.4–6 mm; wings 6.6–9.9 mm long; keel 5.5–7.7 mm long; stipe (0.4–) 0.5–2 mm long; pod 2–4 mm wide; Durango and Chihuahua.................................................................................................................................................... A. ervoides

102. Longest racemes (4–) 6–18 cm long; flowers (13–)20–65 per raceme; pod 3.1–7.8 × 1.8–2.7 mm; Chihuahua, Durango, Nuevo León, Zacatecas, and Aguascalientes............................................................................................................................. A. goldmanii

- Longest racemes 1–4 cm long; flowers 1–7 per raceme; pod (6–) 7–18 mm × 1.6–4.5 mm..........................................................103

103. Stems 30–45 cm long; racemes 8–20 mm long; wings (4–) 4.8–6.3 mm long, its blade 4–4.5 mm long; keel 4–6 mm long; pod (7–)10–21 × 1.6–3.5 mm, curved; Sonora, Chihuahua, Coahuila, Nuevo León, Tamaulipas, Sinaloa, Durango, Zacatecas, Aguacalientes, and San Luis Potosí............................................................................................................................. A. nuttallianus

- Stems up to 15 cm long; racemes 30–40 mm long; wings 4.2–4.6 mm long, its blade 3–3.3 mm long; keel 3.2–3.8 mm long; pod 6–11 × 3–4.5 mm straight; Chihuahua, Coahuila and Zacatecas............................................................................. A. quinqueflorus

104. Pod stipitate; stipe 2–17 mm; Sonora, Durango, San Luis Potosí and Zacatecas..........................................................................105

- Pod sessile; Sonora, Chihuahua, Durango, San Luis Potosí and Zacatecas...................................................................................107

105. Pod ovoid, inflate resembling a bladder, stipe 5–17 mm long; Sonora....................................................................... A. trichopodus

- Pod lanceolate, oblong to elliptic, not inflated not resmebling a bladder, stipe 2–4 mm largo; Durango, San Luis Potosí and Zacatecas........................................................................................................................................................................................106

106. Leaflets (13–)23–29; racemes 1–9.3 cm long with (5–)12–35 flowers; banner 9–11.5 mm long; Durango and San Luis Potosí............................................................................................................................................................................................. A. strigulosus

- Leaflets 9–17; racemes 10–18 cm long with 30–50 flowers; banner 7–9 mm long; Durango and Zacatecas............ A. zacatecanus

107. Peduncles (3–) 9–10 cm long; racemes (1.5–) 3.5–12 cm long; flowers (10–)15–30 per raceme; calyx tube 1.9–3.6 mm wide, its teeth 0.6–2.5 mm long; banner 7.2–9.4 mm long; wings 6.6–8.3 mm long; keel 6.2–7.5 mm long; pod ovoid to semi-elliptic, oblique if it seen if profile, the ventral suture straight or concave, less pronounced than the dorsal one, beak evident and easily differentiated from the body; Chihuahua and Sonora................................................................................................... A. allochrous

- Peduncles 0.5–7 cm long; racemes 1–5 cm long; flowers (2–)5–15 per raceme; calyx tube 1.8–2.3 mm wide, its teeth 2–3.5 mm long; banner 4.6–7.5 mm long; wings 4.1–7.5 mm long; keel 4.1–6.4 mm long; pod ovoid to subglobose, when ovoid, its sides relatively symmetric if they are seen in profile, both sutures, ventral and dorsal, equally convex, beak absent o tiny, not evidently differentiated from the body; Sonora, Chihuahua, Durango, San Luis Potosí and Zacatecas........................................... A. wootonii

108. Stems prostrate, rooting at floral nodes; leaves petiolated, subtending vertical peduncles with respect to soil; mountains of Valle de México, Morelos, and Michoacán..................................................................................................................................................109

- Stems creeping, diffuse, decumbent, prostrate or erect, not rooting in the floral nodes; leaves, except sometimes basal, subsessile; Valley of México and other states..................................................................................................................................................110

109. Stipules 3–5.5 mm long; leaves up to 10 cm long; leaflets 17–26, 4–12 mm long; peduncles 2–7 cm long; mature racemes with 5–12 flowers; banner 11.5–13 (rarely up to 15) mm long; wings 11–12 mm long; most commonly 2900–3330 m alt; México City and State of México.................................................................................................................................................... A. harshbergeri

- Stipules 7–12 mm long; leaves 10.5–30 cm long; leaflets 27–38, 18–28 mm long; peduncles (<10) 20–27 cm long, rarely longer, if shorter than 10 cm, then the racemes with 20 or more flowers; mature racemes with 20–34 flowers; banner 14–15 mm long; wings 12.5–15 mm long; most commonly 2200–2400 m; México City, State of México and Michoacán................................. A. radicans

110. Pubescence dolabriform, the trichomes joined in a point before the end, in the form of “v” or t””, with equal or most frequently with unequal arms......................................................................................................................................................... A. hypoleucus

- Pubescence basifixed, trichomes simple........................................................................................................................................ 111

111. Petals all red; banner 24–33 mm long; endemic of the Cofre de Perote Mountian (Veracruz)............................................ A. helleri

- Petals of different color, or if red, then combined with another color; banner 17.5 mm long or shorter; Veracruz and other states...........................................................................................................................................................................................................112

112. Pod strongly obcompressed, in the form of a car windshield, shield or wing in cross section; Guanajuato and Jalisco............................................................................................................................................................................................................. A. scutaneus

- Pod triquetrous, triangular in cross section, flattened or widened, linear-elliptic, lanceolate, ovate-acuminate, semi-ovate, linearoblong, oblong-elliptic to oblong-obovate, ellipsoid, obovate, ovoid, or inflated resembling a bladder and subglobose, not in shield, or wing shaped in cross section; Jalisco and other states....................................................................................................113

113. Petals pink, rosaceous, purple, lavender, lilac, blue, cherry, violet, purple-reddish, bicolored (even the veins o some part of the petals) or white, but mixed with other color, but not green-whitish or green-yellowish...............................................................114

- Petals all white, cream, yellow, ochroleucous, concolors, if bicolored then green-whitish or green-yellow.................................132

114. Pod triquetrous, inflated-trigonous or trigonous............................................................................................................................115

- Pod linear-elliptic to oblong-elliptic but laterally compressed, ellipsoid-flared or inflated, resembling a bladder.......................124

115. Pod stipitate....................................................................................................................................................................................116

- Pod sessile......................................................................................................................................................................................117

116. Stipe 0.4–2 mm long; leaflets 11–25; banner 6.2–10.2 × 3.4–6 mm; wings 6.6–9.9 mm long; keel 5.5–7.7 mm long; Nayarit, Jalisco and Michoacán................................................................................................................................................................... A. ervoides

- Stipe up to 0.5 mm long; leaflets 17–31; banner 4.4–7 × 3.4–3.5 mm; wings 4.4–4.8 mm long; keel 3.9–4.6 mm long; Michoacán, México City, State of Mexico, Hidalgo, Veracruz, Morelos, Puebla and Oaxaca........................................................ A. micranthus

117. Pod 3.1–6 mm long (rarely to 7.8 mm in Zacatecas); ovules 4–8; racemes 3–18 cm long............................................ A. goldmanii

- Pod (6–) 8–19 mm long; ovules (8–)14–26, or if less than 8, then leaves with 11 or less leaflets or, the racemes only 5–10 mm long.................................................................................................................................................................................................118

118. Racemes (umbrella-like) 5–10 mm long; calyx 2.5–3 mm long, the tube 1.6–2 mm long; pod 7–8 mm long; endemic of Puebla (Esperanza 18°51’47’’N – 97°22’35’’W)............................................................................................................................. A. pueblae

- Racemes (10–) 25–80 mm long, not umbrella-like, or if shorter, then the fruit longer; calyx 3.3–6.3 mm long, the tube 2–3.6 mm long; Puebla and other states..........................................................................................................................................................119

119. Leaflets 7–11 per leaf; calyx teeth 0.6–0.8 mm long; keel 3.2–5 mm long; Jalisco, Hidalgo and Puebla.....................................120

- Leaflets 11–29 or if less than 11, then, the calyx teeth 1 mm long or longer; keel (5–) 5.4–7.7 mm long; Jalisco, Michoacán, City, State of México, Hidalgo and Puebla.............................................................................................................................................121

120. Stems commonly 20 cm long or longer; pod triquetrous, linear, 2 mm wide or narrower, never humistrate; calyx 3.7–5.4 mm long; calyx teeth 0.6–0.7 mm long; wing blade 4–4.3 mm long; keel 4–5 mm long; Hidalgo and Puebla.............................................................................................................................................................................................................. A. nuttallianus var. austrinus

- Stems up to 15 cm long; pod trigonous, somewhat inflated, 3–4.5 mm wide, frequently humistrate wih age; calyx 2–3.6 mm long; calyx teeth 0.8–1.6 mm long; wing blade 3–3.3 mm long; keel 3.2–3.8. mm long; Hidalgo and Jalisco............... A. quinqueflorus

121. Banner 5.1–6.4 mm long; calyx tube 2–2.6 mm long; pod 5–9 mm long; ovules 8–14; City and State of México, Hidalgo and Jalisco......................................................................................................................................................................... A. oxyrhynchus

- Banner 7.4–9.4 mm long; calyx tube (2.2–) 3–3.5 mm long; pod (8–) 11–19 mm long; ovules (12–)14–26; Jalisco, Hidalgo, Michoacán, Guanajuato and Puebla...............................................................................................................................................122

122. Largest racemes 40–140 mm long, flowers (15–)25–62 per raceme; calyx teeth 1–1.4 mm long; Guanajuato, Jalisco, Michoacán, Querétaro......................................................................................................................................................................... A. hartwegii

- Largest racemes 5–30 mm long, flowers (3–)5–25 per raceme; calyx teeth (1.4–) 1.5–3 mm long; Hidalgo, Michoacán and Puebla........................................................................................................................................................................................................123

123. Stipules connate; peduncles (30–) 100–140 mm long; flowers 10–25 per raceme; Hidalgo, Michoacán and Puebla................................................................................................................................................................................................................ A. esperanzae

- Stipules free; peduncles 70 mm long or shorter; flowers 3–12 per raceme; Jalisco and Puebla.......................................... A. parvus

124. Pod sessile......................................................................................................................................................................................125

- Pod stipitate....................................................................................................................................................................................126

125. Leaflets (6–) 12–26 mm long; peduncles (6–) 7–21.5 cm long; calyx 9–13 mm long; banner 15–24.5 mm long; wings 14.5–20.5 mm long; pod 10–25 mm long; ovules 22–28; Jalisco, Guanajuato, Querétaro, Hidalgo, City and State of México, Puebla, Querétaro and Veracruz.......................................................................................................................................... A. mollissimus var. irolanus

- Leaflets (4–) 12–16 mm long; peduncles (3.5–) 4–10.5 cm largo; calyx 3.2–4.6 mm long; banner 5.1–6.4 mm long; wings 5–6.6 mm long; pod 5–9 mm long; ovules 8–14; Jalisco, City and State of México, Hidalgo and Jalisco................................ A. oxyrhynchus

126. Annual; calyx teeth 0.3–0.5 mm long; wing blade 4–4.1 mm long; pod 6–7 mm long; Morelos............................. A. sagitticarpus

- Perennials; calyx teeth 0.7–4.2 mm long; wing blade 5–8 mm long; pod 10–23 mm long; Morelos and other states..................127

127. Banner 6.7–7.8 mm long; wings 6.4–6.9 mm long; keel petals 4.8–5.6 mm long; Guanajuato, and Hidalgo............. A. hidalgensis

- Banner (7.4–) 8.5–15.5 mm long; wings 7.1–13.2 mm long; keel petals 5.8–10.2 mm long; Hidalgo and other states................128

128. Banner 7.4–8.4 mm long; keel 5.8–6.3 mm long; Guanajuato........................................................................................ A. potosinus

- Banner 8.5–15.5 mm long; keel 6.8–10.2 mm long; Guanajuato and other states.........................................................................129

129. Leaflets 2–7 mm long; peduncles 5.5 cm long or shorter; flowers 3–21 per raceme; keel 8.8–10.2 mm long, its blade (4.1–) 4.7–5.4 mm long; Michoacán, State of México and Veracruz........................................................................................................ A. hintonii

- Leaflets (3–) 7–19 mm long; peduncles 5 cm long or longer; flowers (–6)15–30 per raceme; keel 6.8–8.4 mm long, its blade 4–4.6 mm long..........................................................................................................................................................................................130

130. Calyx 3.2–6 mm long; Jalisco, Michoacán, Guanajuato, State of México, Hidalgo, Puebla and Guerrero........................................................................................................................................................................................... A. guatemalensis var. brevidentatus

- Calyx 6.5–7.5 mm long; City y State of México, Chiapas.............................................................................................................131

131. Blade of the wing 1.4–2.4 mm wide; pod 10–15 mm × 4–6 mm; City and State of México; Hidalgo, Michoacán, and Morelos............................................................................................................................................................................................... A. tolucanus

- Blade of the wing 3.8–4.8 mm wide; pod (12–)16–21 × (4–) 6–8 mm; Chiapas..................................................... A. guatemalensis

132. Pod triquetrous o trigonous............................................................................................................................................................133

- Pod linear-elliptic to oblong-elliptic but dorsoventrally compressed, ellipsoid-flared, tumescent or inflated resembling a bladder..........................................................................................................................................................................................................139

133. Pod stipitate....................................................................................................................................................................................134

- Pod sessile......................................................................................................................................................................................136

134. Stipe 2.8–3.1 mm long; calyx tube (2.9) 3.3–4.3 mm long, the teeth 2.3–3.8 mm long; keel 7.7–8.7 mm long, its claw 4–4.7 mm long; mountains of México City, State of México, and Morelos...................................................................................... A. lyonnetii

- Stipe 0.4–1.5 mm long; calyx tube 2.1–3.8 mm long, the teeth 0.7–2.2 mm long, or if longer, then, the blade of the wing petals 3 mm wide or wider; keel 3.9–7.6 mm long, its claw 2–3.7 mm long; México City and other states..............................................135

135. Banner 3–6 mm wide; pod linear-elliptic, 11–18 mm long, stipe (0.4–) 0.6–2 mm long; Nayarit, Jalisco, Michoacán, and Tlaxcala........................................................................................................................................................................................... A. ervoides

- Banner 3–3.5 mm wide; pod oblong-elliptic, (5.5–) 8.5–13 mm largo, stipe 0.1–0.5 mm largo; Michocán, México City and State of México, Morelos, Hidalgo, Puebla, Veracruz y Oaxaca............................................................................................... A. micranthus

136. Mature racemes 4–18 cm long; Guanajuato, Querétaro, and Jalisco.............................................................................. A. hartwegii

- Mature racemes 0.2–2.5 cm long; Guanajuato, Hidalgo, Oaxaca and Puebla...............................................................................137

137. Petals white (if bicolored, white with purple or pink tones); trichomes of stems and foliage 0.4–1.4 mm long; banner 4–7.3 mm long; Hidalgo and Puebla............................................................................................................................................ A. nuttallianus

- Petals yellow-greenish; trichomes of stems and foliage 0.2–0.5 mm long; banner 8–11.2 mm long; confined to local areas of Guanajuato and Oaxaca..................................................................................................................................................................138

138. Most parts of stems subterranean; leaflets 9–15; peduncles 1–2.5 cm long; racemes up to 1 cm long with 7–10 flowers; banner 8–8.5 mm long; keel 6 mm long; pod 8–10 × 4–5.5 mm; ovules 18; Oaxaca....................................................... A. cenorrhynchus

- Most parts (or all) of stems aereal; leaflets 15–27; peduncles 4–6 cm long; racemes 2–3 cm long with 12–18 flowers; banner 9–11 m long; keel 7–8 mm long; pod 10–13 × 2.5 mm; ovules 8; Guanajuato.............................................................. A. guanajuatensis

139. Pod sessile......................................................................................................................................................................................140

- Pod stipitate....................................................................................................................................................................................141

140. Calyx 4.2–6.5 mm long; banner 4.3–7.5 mm long; wings 4.1–7.5 mm long; keel 4.1–6.4 mm long; pod (10–)30–43 × (8–) 12–22 mm, inflated resembling a bladder, valves papery; flowers 2–15 per raceme; State of México, Hidalgo and Veracruz................................................................................................................................................................................................................ A. wootonii

- Calyx 6.8–14 mm long; banner 15–24 mm long; wings 14.2–24.7 mm long; keel 11–14.6 mm long; pod 11–25 × 4–13 mm, flared o inflate but not resembling a bladder, its valves fleshy or leathery or rigid papery; flowers 7–45 per raceme; Jalisco, Guanajuato, Querétaro, City y State of México, Hidalgo, Puebla and Veracruz............................................................................. A. mollissimus

141. Leaflets up to 7 mm long or shorter; peduncles 5 cm or shorter; local species with two disjunct varieties, one in Michoacán and the other in Veracruz................................................................................................................................................................. A. hintonii

- Leaflets commonly longer than 8 (up to 22 mm); peduncles 6 cm or longer................................................................................142

142. Larger leaflets up to 8 mm long; calyx 3.4–4.5 mm long, the tube 2.3–2.7 mm long; banner 6.7–7.8 mm largo; wings 6.4–6.9 mm long; keel 4.8–5.6 mm long; endemic of Hidalgo........................................................................................................ A. hidalgensis

- Leaflets larger than 8 mm long, up to 20 mm long; calyx (4–) 5–7.8 mm long, the tube (2.6–) 2.8–4 mm long; banner (7–) 8.5–12 mm long; wings 7.7–10.5 mm long; keel 6.2–8.5 mm long; Hidalgo and other states..................................................................143

143. Racemes 9.5–18 cm long; banner 7–9 mm long; blade of the wing petals 1.5 mm wide; keel 6.2–7 mm long; Durango, Jalisco and Zacatecas..................................................................................................................................................................... A. zacatecanus

- Racemes 0.5–9 cm long; banner (8.5–) 9.5–12 mm long; blade of the wing petals 1.8–2.8 mm wide; keel 6.7–8.3 mm long; Jalisco and other states, but not in Durango and Zacatecas.......................................................................................................................144

144. Pod oblong-elongate, 1.6–3.8 × 0.4–0.7 cm, almost 4 to 5 times longer than wide; Jalisco and Nayarit...................... A. jaliscensis

- Pod wide oblong, shorter, but relatively borader, 1.2–2 × 0.4–0.8 cm; wider distributed.............................................................145

145. Plant erect; pod dorsally and basally dehiscent only; trichomes of stems and foliage 0.4–0.7 mm long; peduncles (4–) 5–10 cm long; calyx tube 2.6–3.2 mm long; wing claw 3–3.5 mm long; keel 6.7–7.5 mm long; Jalisco, México City and State of México, Tlaxcala, Hidalgo, Puebla and Oaxaca.......................................................................................................................... A. strigulosus

- Plants diffuse or trailing; pod dorsally dehiscent in all its length, trichomes of stems and foliage 0.2–0.3 mm long; peduncles (3–) 15–26 cm long; calyx tube 2.6–4 mm long; wing claw 3.2–4.6 mm long; keel 6.8–8.3 mm long; Jalisco, Michoacán, Guanajuato, State of México, Morelos, Hidalgo, Puebla, Guerrero, Oaxaca and Chiapas......................................................... A. guatemalensis