6.01 BRACHYELYTRUM P. Beauv.
Stephen N. Stephenson
Jeffery M. Saarela
Plants perennial; rhizomatous, rhizomes knotty. Culms 28–102 cm, erect, not branched above the bases; internodes solid; nodes glabrous or retrorsely pubescent. Leaves mostly cauline; sheaths open; auricles absent; ligules membranous; lower leaf blades absent or reduced; upper leaf blades flat, tapering both basally and apically. Inflorescences terminal panicles, contracted; branches appressed, with 1–3(5) spikelets. Spikelets pedicellate, terete to dorsally compressed, with 1 floret; rachillas prolonged beyond the floret base, glabrous; disarticulation above the glumes, beneath the floret. Glumes 1 or 2; lower glumes 0.1–1.1 mm, sometimes absent; upper glumes 0.2–7 mm, clearly exceeded by the florets; florets 8–12 mm; calluses about 0.8 mm, blunt, with hairs; lemmas membranous to coriaceous, scabrous, enclosing the paleas, 5-veined, tapering, awned, awns terminal, lemma-awn transition gradual; awns 9.5–32.5 mm, longer than the lemma bodies, straight, scabrous; paleas subequal to the lemmas, 2-veined; lodicules 2, veined; anthers 3, yellow; styles 2, bases free, white. Caryopses linear, longitudinally grooved, apices beaked, pubescent; hila linear. x = 11. Name from the Greek brachys, ‘short’, and elytron, ‘husk’ or ‘involucre’, a reference to the short glumes.
Brachyelytrum includes three species, two native to eastern North American and one to eastern Asia (Saarela et al. 2003). The ranges of the two North American species overlap but, although they often grow closely together, neither mixed populations nor apparent hybrids have been found (Stephenson 1971; Saarela et al. 2003). Saarela et al. (2003) were unable to detect any differences in the ecological preferences of the two North American taxa.
SELECTED REFERENCES Campbell, C.S., P.E. Garwood and L.P. Specht. 1986. Bambusoid affinities of the north temperate genus Brachyelytrum (Gramineae). Bull. Torrey Bot. Club 113:135–141; Koyama, T. and S. Kawano. 1964. Critical taxa of grasses with North American and eastern Asiatic distribution. Canad. J. Bot. 42:859–884; Saarela, J.M., P.M. Peterson, R.J. Soreng, and R.E. Chapman. 2003. A taxonomic revision of the eastern North American and eastern Asian disjunct genus Brachyelytrum (Poaceae): Evidence from morphology, phytogeography and AFLPs. Syst. Bot. 28:674–692; Stephenson, S.N. 1971. The biosystematics and ecology of the genus Brachyelytrum (Gramineae) in Michigan. Michigan Bot. 10:19–33.
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1. Lemmas hispid, hairs 0.2–0.9 mm long, visible at 10× magnification; anthers 3.5–6 mm long; awns 13–17(20) mm long ... B. erectum
1. Lemmas scabrous, scabrules 0.08–0.14(0.2) mm long; anthers 2–3.5 mm long; awns (14)17–24(26) mm long ... B. aristosum
1. Brachyelytrum erectum (Schreb.) P. Beauv.
Southern Shorthusk, Brachyelytrum Dressé
Culms 34–102 cm long, 0.7–1.4 mm thick, erect; nodes densely pilose; lowest internodes mostly glabrous, usually retrorsely pub-escent near the nodes. Sheaths hispid; ligules of middle and upper cauline blades 2–3.5 mm, truncate to acute, lacerate or erose; blades 8.8–17.5 cm long, (9)11–17(20) mm wide, abaxial surfaces pilose on the veins and often between the veins, adaxial surfaces glabrous or slightly hispid, margins scabrous, with (2)5–11(14) prickles and 0–2(14) macrohairs per mm. Panicles (5.5)9.1–14.3(18.5) cm. Spikelets, including the awns, (25)29–36(42) mm. Lower glumes (0.1)0.3–0.7(1.1) mm, sometimes absent; upper glumes (0.2)0.9–3.5(7) mm, sometimes aristate; calluses hairy, hairs 0.2–0.5 mm; lemmas 9–13 mm long, 0.8–1.7 mm wide, veins hispid, hairs 0.2–0.9 mm, midveins more prominent than the lateral veins; awns 13–17(20) mm; paleas 7–12 mm; anthers 3.5–6 mm. Caryopses 5.5–7.5 mm. 2n = 22.
Brachyelytrum erectum grows in woodlands, occasionally over limestone bedrock, and in moist woods and forests. It extends from Lake of the Woods, Ontario, east to Newfoundland, and in the United States from Minnesota to New England and south to the Gulf Coast and Florida.
Koyama and Kawano (1964), among others, treated Brachyelytrum erectum var. glabratum (Vasey) T. Koyama & Kawano as the northern taxon B. aristosum, but the holotype of B. erectum var. glabratum belongs to B. erectum sensu stricto. This means that, nomenclaturally, B. erectum var. glabratum is a synonym of B. erectum, although most of the specimens identified as var. glabratum belong to B. aristosum.
2. Brachyelytrum aristosum (Michx.) P. Beauv. ex Branner & Coville
Culms (28)41–78(96) cm long, 0.6–1 mm thick; nodes densely pilose; internodes glabrous or hispid, occasionally retrorsely pubescent near the nodes. Sheaths pubescent; ligules of middle and upper cauline blades 1.8–2.5 mm, acute, erose; blades (6.9)8.6–13 (16.1) cm long, 8–16 mm wide, abaxial surfaces sparsely pilose, adaxial surfaces with some hairs usually restricted to the veins, margins scabrous, with (1)4–10(12) prickles and (1)1–9 macrohairs per mm. Panicles (6.6)9.5–17.5 cm. Spikelets, including the awns, 23–36 mm. Lower glumes 0.1–0.4(0.9) mm, sometimes absent; upper glumes 0.6–1.7(3) mm; calluses hairy, hairs 0.2–0.5 mm; lemmas 8–10(11) mm long, 0.7–1.4 mm wide, veins scabridulous, scabrules 0.08–0.14(0.2) mm, all veins equally prominent; awns (14)17–24(26) mm; paleas 7.7–11.5 mm; anthers 2–3.5 mm. Caryopses 5.5–7.5 mm. 2n = 22.
Brachyelytrum aristosum, like B. erectum, grows in moist woods and forests, but its primary distribution is more northern, extending from Ontario to Newfoundland, Minnesota, and Pennsylvania, and south through the Appalachian Mountains to the junction of Tennessee, North Carolina, and Georgia.
Some authors (e.g., Koyama and Kawano 1964) have called this taxon Brachyelytrum erectum var. glabratum. As discussed under B. erectum, that name is a nomenclatural synonym of B. erectum sensu stricto. Nevertheless, most plants identified as B. erectum var. glabratum will be found to be B. aristosum.