Trigonochloa rupestris (C.E. Hubb.) P.M. Peterson & N. Snow. Ann. Bot. 109: 1328. 2012.

Snow, Neil & Peterson, Paul M., 2012, Systematics of Trigonochloa (Poaceae, Chloridoideae, Chlorideae), PhytoKeys 13, pp. 25-38 : 29-30

Trigonochloa rupestris (C.E. Hubb.) P.M. Peterson & N. Snow. Ann. Bot. 109: 1328. 2012. Figure 1A-E

Leptochloa rupestris C.E. Hubb., Bull. Misc. Inform. Kew: 195. 1941.

Type.

SOMALIA. Mt. Wobleh, J.B.Gillett 4981(holotype: K!; isotype: K!)

Description.

Plants perennial. Culms 35-85 cm tall, 0.7-1.4 mm wide at base, decumbent or sprawling-stoloniferous to erect, often arising from a thick root crown, branching (often profusely); internodes (0.7-)2.0-5.5(-8.5) cm long, soft to strongly lignified. Leaf sheaths longer or shorter than internodes, glabrous on sides but sometimes minutely papillate at high magnification, margins ciliate (trichomes <1 mm long); collar green; ligules 1.0-2.5 mm long, truncate or obtuse; blades 2.2-5.5(-10.7) cm long, 0.3-4.0(-5.0) mm wide, linear to narrowly ovate, glabrous above, glabrous below but sometimes densely minutely papillate, midrib prominent. Panicles 17-35 cm long, 2.0-4.5 cm wide with 13-66 branches, the branches (1.5-)2.0-4.5 cm long, minutely scabrous, the axils glabrous or at most scabrous and more or less short pilose on the exterior. Spikelets 2.0-2.8 mm long, 1-flowered, nearly sessile or with minute pedicels, more or less imbricate, callus area glabrous; lower glumes 2.4-3.1 mm long, membranous, lanceolate, midnerve scabrous, apex acute to acuminate; upper glumes, 2.2-2.8 mm long, otherwise like lower glumes; lemmas 1.2-2.1 mm long, ovate, light green or nearly white, the lateral nerves faint, sericeous along midnerve (use high magnification), the hair tips rounded, apex acute and awnless; paleas 1.6-2.0 mm long, hyaline, narrowly ovate, glabrous or sparsely sericeous near nerves, apex acute to obtuse; anthers 1.0-1.4 mm long, yellow to brownish green. Caryopses ca. 1.0 mm long and 0.4 mm wide, trigonous in cross section, the surface smooth.

Phenology.

Flowering June through January.

Distribution.

This species is found in Yemen and Eritrea south to Kenya in woodlands, hillsides, bushland and on damp rocks along streams; 900-1800 m. [Taxonomic Database Working Group (TDWG): 24: ERI, ETH, SOM; 25: KEN, UGA].

Conservation status.

Since many parts of its range are presently inaccessible to botanists or still remain inadequately surveyed this species is data deficient. Additional observations and collections are highly desirable.

Etymology.

The epithet rupestis is Latin for "of rocks", presumably in reference to observations of the habitat of the type collection.

Vernacular name.

Somalian triangle-seed grass.

Comments.

This species closely resembles Trigonochloa uniflora , with which it is morphologically similar. The best character to recognize Trigonochloa rupestris from Trigonochloa uniflora is leaf blade width. However, its sprawling, branching, and perennial growth form with narrow culms typically distinguish it from Trigonochloa uniflora . The holotype and isotype are aberrant in their lack of ciliate sheath margins, but otherwise accord with the diagnostic characters. The observation of Phillips (1974) that Trigonochloa rupestris has more widely divergent leaf blades than Trigonochloa uniflora cannot be reliably applied to dried material. None of the specimens we have seen confirmed her observation ( Phillips 1974) that Trigonochloa rupestris is rhizomatous (i.e., culms within the soil), but the stems can be somewhat sprawling and stoloniferous.

Specimens examined.

Eritrea. Donkollo, Schweinfurth 207 (P); Dongollo Presso Ghinda, Pappi 2821 (MO); Monte Dijot, Pappi 2940 (US). Ethiopia. Gamo Gofo: 44 km from Jinka on raod to Konso, ca. 3 km E of K’ey Afer, Gilbert et al. 8954(K); 13 km N of Lante, 29 km N of Arba Minch, Gilbert et al. 8874 (K). Arba Minch, Gilbert et al. 249 (K, MO). Harar:"Rock Valley", 36 km along the road from Harrar to Jijiga, Amshoff 5520 (B, MO); Errer valley, 22 km SE of Harar on hwy to Djigdjigga, Burger 1162 (K); 7 km from Harar towards Jijiga, Gilbert & Gilbert 1443(K). Sidamo:Between the Genale Doria bridge and the main road Kebre Mengist-Neghelle, on the Biderre track, Friis et al. 1034 (K). Kenya. Rift Valley:West Suk Reserve, 30 mi N of Kitale, Bogdan 3429 (K); West Suk Reserve, 10 mi W of Kapenguria, Suam Riv. Valley, Bogdan 289(K); West Suk, Marech Pass, 40 mi N of Kapenguria, Bogdan 3844(K); 30 mi N of Nakuru, Bogdan 4891 (K, US); Kenya Grassland Research Station, Bogdan AB3964 (P). Somalia. "WOGR near Sheikh", Wood S/72/95 (K); Jifa Uri, Gillett 4838 (K, US). Uganda.Northern: Moroto Mountains, Karamoja, Napper 1509(K); Warr, Karamoja, Thomas 3176(K). Yemen. Habash, Jebel Melhan, Wood 2848 (BM, K); 2 mi W of Mefhek, Wood Y/75/727 (BM); by Wadi Dur, Udayn, Wood 2000 (K, US).

Figures

Figure 1. Trigonochloa rupestris (C. E. Hubb.) P. M. Peterson & N. Snow A Habit B Inflorescence C Portion of inflorescence branch D Spikelet E Floret. Drawn from Wood 2000.