1. Galium acutum Edgeworth, Trans. Linn. Soc. London. 20: 61. 1846.
尖瓣拉拉藤 jian ban la la teng
Herbs, perennial, procumbent, much branched, mat-forming. Stems up to 30 cm, 4(or 6)-angled, glabrous, smooth or sometimes with scattered (very rarely more dense) short and straight hairs. Leaves in whorls of up to 6, sessile; blade drying papery and blackish, linear-oblanceolate to narrowly elliptic-oblanceolate, 2-8.5 × 0.3-1.5 mm, glabrous and smooth, occasionally with straight hairs, base cuneate, margins flat to thinly revolute, very rarely antrorsely aculeolate, apex acute, ± contracted and mucronate; vein 1. Inflorescences with terminal and axillary cymes, 1- to few flowered; peduncles (1.5-)3-8(-10) mm; pedicels (0.1-)0.5-2(-3) mm, glabrous, smooth. Ovary ellipsoid-obovoid, ca. 0.5 mm, didymous, glabrous. Corolla white, pale greenish, or yellowish, rotate, 1.2-3.5 mm in diam., glabrous to puberulent, lobed for 2/3 or more; lobes 4, lanceolate-spatulate, inside (i.e., adaxially) papillose, shortly acuminate. Mericarps ellipsoid, ca. 1 × 0.4-0.6 mm, glabrous, smooth or granular-verruculose, often on elongating pedicels. Fl. and fr. Jul-Oct.
Mountain rocks and slopes; 2000-4100 m. ?Sichuan, Xizang, ?Yunnan [India, Nepal, Pakistan].
Galium acutum is a (sub)alpine Himalayan member of the G. asperifolium group (see under that species). This group of taxa can be divided into subgroups: (1) from lower elevations and (2) from higher elevations. The latter subgroup is represented in the W Himalaya of Pakistan by G. acutum alone (Nazimuddin & Ehrendorfer, Pl. Syst. Evol. 155: 71-75. 1987). Mill (Edinburgh J. Bot. 53: 193-213. 1996; Fl. Bhutan 2(2): 825-834. 1999) has analyzed both subgroups in detail with emphasis on their E Himalayan members. Among subgroup (2) he recognized three species: G. acutum and the newly described G. rebae and G. megacyttarion. The only material from China incorporated in Mill’s study are specimens of G. rebae from Xizang deposited at E and BM. Additional species from subgroup (2) from the C and E Himalaya and adjacent China treated here are G. baldensiforme, G. pusillosetosum, G. glabriusculum, and G. sungpanense. They appear well separable from G. acutum.
Galium acutum and G. rebae are very closely related taxa. Mill (loc. cit. 1996: 199) presented a differential table which has been incorporated into the present descriptions. Nevertheless, from the material available now, it appears that only flower color (white or greenish white in G. acutum and reddish crimson in G. rebae) is really decisive for their separation. Furthermore, at lower elevations, G. acutum appears linked to G. asperifolium var. sikkimense. Cufodontis (Oesterr. Bot. Z. 89: 239. 1940) has described such transitional forms with longer and ± retrorsely aculeolate stems and hairy corolla lobes from the Indian Himalaya as G. acutum var. trichanthum Cufodontis.
Mill (loc. cit. 1996: 194-198) considered Galium acutum to be restricted to the NW Himalaya except for one provisionally identified specimen from Sikkim. In contrast, specimens studied by us from the herbaria PE, KUN, and WU clearly show that G. acutum extends much further to the east, reaching Yunnan and Sichuan.
Galium himalayense was regarded as a synonym of G. acutum by Cufodontis (loc. cit.: 239-243). Mill (loc. cit. 1996: 195; loc. cit. 1999: 831-832) agreed but maintained the taxon as G. acutum var. himalayense and described its sympatric occurrence with G. acutum var. acutum throughout the NW Himalaya. As Mill did not consider the possible occurrence of flower dimorphism in G. acutum, it remains uncertain whether the flower and stigma size differences listed are possibly correlated with male and female plants or simply correspond to hermaphroditic variants within the morphological amplitude of the species. In order to stimulate such studies and to clarify the distribution of the two taxa in China, a key and descriptions (according to Mill, loc. cit. 1996) follow: