Epilobium L.

3. Epilobium L., pro parte.

Lectotype (designated by Britton & Brown 1913):— Epilobium hirsutum Linnaeus (1753: 347).

Herbs perennial or annual, erect to ascending or decumbent, with leafy rosettes, stolons, soboles, or turions. Stems glabrous to pubescent, some species with 2–4-lines of strigillose decurrent from margins of petioles. Leaves subsessile to petiolate, opposite and decussate, becoming alternate and in inflorescence; lanceolate to ovate, sometimes to sublinear. Flowers 4-merous, actinomorphic or rarely zygomorphic, with floral tube, the base of style has nectar; petals rose-purple to white, obcordate or obtrullate, apically notched; stamens 8, in two unequal series; ovary with 4 locules, stigma erect, entire or deeply 4-lobed. Fruit pedicellate or sessile, 4-loculed. Seeds with coma. Chromosome number: 2n = 36 (Chen et al. 1992).

The genus Epilobium is the largest one in the family, comprising 165 species (185 taxa) (Wagner et al. 2007). The monophyly of the strictly defined Epilobium (with exclusion of Chamaenerion) was strongly supported (100% BS) by analyses of the nrITS region (Baum et al. 1994) and nrITS plus trn L-F regions (Levin et al. 2003). It was divided into eight sections according to the new classifications (Wagner et al. 2007). In the Pan-Himalaya region, there are 35 species (37 taxa) of Epilobium, all of which are in the same section (E. sect. Epilobium).

Key to species of Epilobium in the Pan-Himalaya region

1 Stigma deeply 4-lobed........................................................................................................................................................................2

- Stigma entire or shallowly emarginate ...............................................................................................................................................5

2 Stems with long spreading villous pubescent and short erect glandular hairs ...................................................................................3

- Stems strigillose, without long villous pubescent ..............................................................................................................................4

3 Petals (7–) 10–20 mm; stigma exserted beyond anthers ........................................................................................... 3.13. E. hirsutum

- Petals 5–8 mm; stigma surrounded by anthers .................................................................................................... 3.22. E. parviflorum

4 Petals 5–7.5 mm; leaves obovate to oblanceolate ............................................................................................................3.3. E. blinii

- Petals 6–8 mm; leaves lanceolate-linear.................................................................................................................. 3.28. E. staintonii

5 Stem with densely strigillose throughout ..........................................................................................................................................6

- Stem glabrous, with strigillose lines on internodes, decurrent from margins of petioles, sometimes lines not obvious .................16

6 Leaves narrowly lanceolate to sublinear, or lanceolate-elliptic, length is more than 5 times the width ............................................7

- Leaves elliptic to ovate (or short lanceolate), length is less than 5 times the width ..........................................................................9

7 Leaves margin denticulate .......................................................................................................................... 3.23. E. platystigmatosum

- Leaves margin subentire.....................................................................................................................................................................8

8 Leaves lanceolate-elliptic to lanceolate-oblong; petals white, 3–4(–4.7) mm; coma tawny.................... 3.10. E. fastigiatoramosum

- Leaves sublinear to narrowly lanceolate; petals white to pink, 3–7(–9) mm; coma white or rarely tawny.............. 3.20. E. palustre

9 Flower 7–16 mm ...............................................................................................................................................................................10

- Flower 3–7.2 mm ..............................................................................................................................................................................12

10 Stem densely appressed-tomentose, sometimes mixed with glandular hairs on inflorescence..............................3.21. E. pannosum

- Stem densely glandular and strigillose throughout ..........................................................................................................................11

11 Leaves margin sharply serrulate with 28–42(–60) teeth; capsules 7–11 cm ........................................................... 3.15. E. kermodei

- Leaves margins more or less sharply denticulate with 7–22 teeth; capsules 3.5–7 cm long..................................3.4. E. brevifolium

12 Stems with brown basal scales .........................................................................................................................................................13

- Stems without brown basal scales ....................................................................................................................................................15

13 Stems mostly shorter than 20 cm; leaves apex acute, subsessile .....................................................................................................14

- Stem 15–40 cm; leaves apex subobtuse or acute, petiole 1–4 mm .................................................................................3.9. E. fangii

14 Upper internodes elongate, exceeding 3 times leaf length .................................................................................... 3.7. E. clarkeanum

- Internodes subequal, slightly longer than leaves..............................................................................................3.32. E. trichophyllum

15 Petals 3–4.3 mm ................................................................................................................................................ 3.19. E. minutiflorum

- Petals 5–7.2 mm .................................................................................................................................................... 3.25. E. royleanum

16 Petiole obvious more than 2 mm ......................................................................................................................................................17

- Leaves subsessile, or only about 2mm in the lower part of the plant...............................................................................................22

17 Leaves often crowded and spirally arranged on mid-stem......................................................................................... 3.27. E. sinense

- Leaves opposite below inflorescence ...............................................................................................................................................18

18 Stems 13–100 cm tall .......................................................................................................................................................................19

- Stems shorter than 35 cm .................................................................................................................................................................21

19 Petals 3–8 mm ..................................................................................................................................................................................20

- Petals 10–11 mm ....................................................................................................................................................... 3.14. E. indicum

20 Leaves margin serrulate with 15–35 teeth per side, lanceolate to narrowly ovate; seeds 1.1–1.3 mm .................. 3.31. E. tibetanum

- Leaves margin densely serrulate with (20–)30–50 teeth per side, narrowly lanceolate to sublinear; seeds 0.8–1 mm ....................... ............................................................................................................................................................................... 3.8. E. cylindricum

21 Underground stems with brown coriaceous scales.................................................................................................. 3.1. E. aitchisonii

- Stems base with stolons, without scales ................................................................................................................ 3.34. E. wattianum

22 Plants completely glabrous, and strigillose lines is absent.................................................................................. 3.18. E. leiophyllum

- Stem glabrous, with (2 or)4 raised strigillose lines on internodes ...................................................................................................23

23 Stem with brown coriaceous scales..................................................................................................................................................24

- Stem without brown coriaceous scales.............................................................................................................................................32

24 Flower 6–14 mm ...............................................................................................................................................................................25

- Flower less than 3.5–6.5 mm ............................................................................................................................................................29

25 Herbs with soboles ...........................................................................................................................................................................26

- Herbs with fleshy turion ...................................................................................................................................................................27

26 Seeds gray-brown, 1–1.3 mm ................................................................................................................................3.26. E. sikkimense

- Seeds dark brown, 1.4–1.6 mm ............................................................................................................................... 3.16. E. kingdonii

27 Leaves alternate above, margin sharply denticulate.........................................................................................................................28

- Leaves nearly all opposite, obscurely serrulate......................................................................................................... 3.11. E. glaciale

28 Leaves ovate, 2–7×1.2–2.6........................................................................................................................................... 3.17. E. laxum

- Leaves subleathery, narrowly ovate to lanceolate, 1.5–5.5×0.5–1.5 ................................................................3.30. E. subcoriaceum

29 Stigma clavate to subcapitate ......................................................................................................................................3.12. E. gouldii

- Stigma capitate .................................................................................................................................................................................30

30 Stem often well branched from the base, a dense tuft of coriaceous brown scales..........................................................................31

- Stem usually unbranched from the base, and the scales sparse......................................................................3.5. E. brevisquamatum

31 Pubescence of inflorescence with a conspicuous admixture of glandular hairs..................................................... 3.35. E. williamsii

- Pubescence of inflorescence entirely strigose ........................................................................................................ 3.6. E. chitralense

32 Stigma capitate to broadly clavate....................................................................................................................................................33

- Stigma clavate .................................................................................................................................................3.29. E. stracheyanum

33 Stem somewhat 4-angled, with (2 or)4 raised strigillose lines on internodes .................................................. 3.33. E. wallichianum - Stem with 2 raised strigillose lines on internodes ............................................................................................................................34

34 Herb erect, with leafy basal soboles, elongated rosettes, or rarely fleshy stolons; stigma capitate or broadly capitate ...................... ...................................................................................................................................................................................3.2. E. amurense

- Herb with turion; stigma capitate to broadly clavate...................................................................................3.24. E. rhynchospermum