Thalictrum angustialatum Y. P. Zeng, Q. Yuan & Q. E. Yang

Thalictrum angustialatum (Wang in Wang & Wang 1979a: 618) Y.P. Zeng, Q. Yuan & Q.E. Yang, comb. & stat. nov.

Figs. 1‒3, 7A‒D, 11, 12.

≡ T. uncatum var. angustialatum Wang in Wang & Wang (1979a: 618), syn. nov.

≡ T. uncatum subsp. angustialatum (Wang in Wang & Wang 1979a: 618) Luferov (2014: 147), syn. nov.

Type:— CHINA. Guizhou: Weining, Jiali village, stream side, alt. 2550 m, 9 July 1959, Bijie Exped. 125 [holotype PE01040628!; isotypes HGAS013441!, PE (barcode unavailable)!]. Fig. 1.

Description:—Perennial herbs, glabrous throughout. Roots fibrous. Stem 60–150 cm tall. Basal leaves persistent at anthesis. Cauline leaves 2–4-ternate; leaf blade triangular, 8–15 cm long, 8–13 cm broad; leaflet obovate, obtriangular or ovate, 0.8–1.8 cm long, 0.5–1.5 cm broad, base rounded or subcordate, apex obtuse, shallowly 3-lobed; lobe usually entire, apex obtuse; petiole 1–8 cm long; stipule sheath-like or oblong, membranous, margin entire; stipel broadly ovate, membranous, margin entire. Inflorescence a panicle, racemelike. Flowers bisexual, drooping. Sepals 4‒5, broadly ovate, 4–5 mm long, 3‒3.5 mm broad, purplish-green. Stamens 20‒25, 5‒7 mm long; filament filiform, 2‒3.5 mm long, purplish; anther 3‒3.5 mm long, oblong, yellowish. Carpels 10–15, sessile; ovary compressed ellipsoid; style 2.5‒2.8 mm long, straight; stigma oblong, narrowly winged, usually purplish. Achenes 10–15, ca. 1 cm long, shortly stipitate; stipe ca. 1 mm long; body lunate, ca. 7 mm long, 2.5‒3 mm broad, compressed, profoundly ribbed; style persistent, slightly curved at apex.

Phenology:—Flowering from May to June; fruiting from June to August.

Distribution and habitat:— Thalictrum angustialatum is endemic to China (western Guizhou, southwestern Sichuan, northeastern and northwestern Yunnan) (Fig. 8). It grows in forest margins, bushes, grasslands in ravines or on slopes at elevations of 1800–3500 m above sea level.

Additional specimens examined:— CHINA. Sichuan: Ganluo, Anonymous 319 (SM704604655); Huidong, Huidong Exped. 220 (SM704604953); Leibo, Anonymous 110511 (SZ00092715), Leibo Exped. 206 (SM704604651, SM704604652), Q.S. Zhao & Z.J. Zhao 121466 (CDBI0026465); Meigu, Anonymous 13088 (CDBI0026388, CDBI0026389, CDBI0026396, PE01040627), Anonymous 13126 (CDBI0026393, CDBI0026394, CDBI0026395, PE00427839), X.J. He & Q.S. Zhao 169722 (SZ00578409, SZ00578410, SZ00578419, SZ00578431), X.J. He, Q.S. Zhao & Q. Wang 151155 (SZ00377950, SZ00377951, SZ00377952), X.J. He, Q.S. Zhao & Q. Wang 151579 (SZ00375252, SZ00375253, SZ00375254), X.J. He, Q.S. Zhao & Q. Wang 151816 (SZ00375265, SZ00375266, SZ00375313, SZ00375356), X.J. He, Q.S. Zhao & Q. Wang 168879 (SZ00578405, SZ00578406, SZ00578407, SZ01104754), Sichuan Econ. Plant Exped. 1057 (PE00451764); Muli, Anonymous s.n. (HITBC, herb. no. 074342), H.B. Chen 87033 (PEM0002853), Muli Exped. 52 (SM704604658), C. Schneider 1170 (E, K), C. Schneider 1382 (E), T.T. Yu 5706 (KUN0689917, KUN0689918, PE00471167, PE00471169), T.T. Yu 14335 (E, KUN0690361); Puge, Sichuan Med. Plant Exped. 25061 (NAS, SM704604653); Xide, Anonymous 295 (SM704604656, SM704604657), Anonymous 465 (SM704604952), X.J. He & Q.S. Zhao 184430 (SZ00578404, SZ00578403); Zhaojue, Anonymous 12823 (CDBI0026391, CDBI0026392, CDBI0026408, PE00427838), Zhaojue Exped. 458 (SM704604951). Yunnan: Dongchuan, E.E. maire s.n. (E00386256, GH00038610, P00147424), E.E. Maire 43 (BM, IBSC0090354), E.E. maire 902 (E), E.E. Maire 7443 (NAS, NY02859465); Huize, W.Q. Fei & H.S. Wu 313 (IBSC); Ninglang, Y.P. Zeng & Y.F. Luo 498 (IBSC); Qiaojia, X.Q. Guo 50 (IBSC), Y.P. Zeng & Q.L. Huang 315 (IBSC).

Notes:—We have traced four duplicates of the type collection of Thalictrum angustialatum, Bijie Exped. 125, and found that one of the three PE sheets with the barcode PE00471121 (Fig. 10) actually belongs to T. lecoyeri Franchet (1889: 16), not T. angustialatum. Obviously Wang in Wang & Wang (1979a) did not use this sheet when he described T. uncatum var. angustialatum as new, because he had correctly identified it as T. lecoyeri on the determination slip and later cited it under T. lecoyeri var. lecoyeri (Wang 2018). Morphologically T. lecoyeri is remarkably different from T. angustialatum by an array of characters. In T. lecoyeri, the plant is glandular pubescent throughout, inflorescence is a nearly flat-topped panicle, flowers are erect, sepals are purplish green, caducous, filaments are white, and styles are circinate. As all the plants on another three sheets (one at HGAS, two at PE) are in fruit, the collectors should have recorded the color of the flowers of this collection as white according to the flowering and fruiting specimen of the PE sheet of T. lecoyeri mentioned above. In fact, flowers of T. angustialatum are not white, but purplish- green (Fig. 2H). Those of T. lecoyeri are also purplish-green, but the sepals have fallen in the PE sheet in question; actually only the somewhat petaloid stamens are white (Franchet 1889).

Wang & Wang (1979b) and Wang (2018) placed Thalictrum uncatum var. angustialatum and T. uncatum var. uncatum within T. ser. Uncata Wang & Wang (1979a: 617) under T. sect. Leptostigma Boivin (1944: 360). In our opinion, T. uncatum var. angustialatum (= T. angustialatum), with a long and straight style which is slightly recurved at apex when mature, just as that of T. sinomacrostigma, should be a member of T. ser. Sinomacrostigma Wang (2018: 242) under T. sect. Rutifolia (Prantl 1887: 271) Wang (2018: 234). That is to say, T. angustialatum may be more closely related to T. sinomacrostigma than to T. uncatum from a morphological perspective. This has also been supported by our cytological and molecular systematic data.

Most of the specimens of Thalictrum angustialatum have been previously misidentified as T. uncatum (Fig. 11) or, less often, as T. leuconotum (Fig. 12). Morphologically T. angustialatum differs from T. leuconotum by its carpels sessile (vs. stipitate, with the stipe ca. 1 mm long) (Figs. 2K, 4K), carpels more numerous (10‒15 vs. 1‒6, occasionally absent) (Figs. 2L, 4L), stipe of achenes ca. 1 mm (vs. 1.8‒2.5 mm) long, and persistent style slightly curved at apex (vs. ventrally reflexed at base) (Figs. 2M, 4M) (Zeng et al. 2020, 2021, 2022).

To facilitate the identification of specimens of Thalictrum angustialatum and its morphologically similar species, including T. leuconotum, T. sinomacrostigma and T. uncatum, a diagnostic key to them is given below.