17.37 ENTEROPOGON Nees

Mary E. Barkworth

Plants annual or perennial; cespitose, sometimes stoloniferous or rhizomatous. Culms to 120 cm, not woody. Sheaths open; ligules membranous, ciliate; blades flat. Inflorescences terminal, panicles of 1-20 non-disarticulating, spikelike branches, exceeding the upper leaves; branches digitately or racemosely arranged, if racemose, the lower nodes usually with more than 1 branch. Spikelets solitary, strongly imbricate, appressed to somewhat divergent, dorsally compressed, with 2-6 florets, lowest floret bisexual, elongate, remaining florets progressively reduced, usually the distal florets rudimentary and sterile, occasionally staminate; disarticulation beneath the glumes. Glumes unequal, subulate to lanceolate, membranous; upper glumes much shorter than the lowest florets, acute or shortly awned; calluses strigose; lowest lemmas stiff, 3-veined, ridged over the midveins, apices acute or bidentate, usually awned from between the teeth, without lateral awns; paleas almost as long as the lemmas, 2-keeled and bidentate; distal lemmas awned; lodicules 2; anthers 1-3. Caryopses sulcate; embryos 1/4-1/3(1/2) as long as the caryopses. x = 10. Name presumably from the Greek enteron, intestine and pogon, beard, although the allusion is unclear.

Enteropogon is a tropical genus of 17 species. Anderson (1974) included it in Chloris, but it is now usually recognized as a separate genus. It differs from Chloris in its dorsally compressed, indurate lemmas that are conspicuously ridged over the midvein. The caryopses also differ, being dorsally flattened with a shallow ventral groove in Enteropogon; in Chloris, the caryopses are basically triangular in cross section although there may be a shallow ventral groove. The embryos also tend to be shorter relative to the caryopses in Enteropogon than in Chloris, but there is some overlap.

There is one species native to the Flora region; two others have been found at various locations but have not persisted.

SELECTED REFERENCES Anderson, D.E.1974. Taxonomy of the genus Chloris (Gramineae). Brigham Young Univ. Sci. Bull., Biol. Ser. 19:1-133; Jacobs, S.W.L. and J. Highet. 1988. Re-evaluation of the characters used to distinguish Enteropogon from Chloris (Poaceae). Telopea 3:217-221; Lazarides, M. 1972. A revision of Australian Chlorideae (Gramineae). Austral. J. Bot. (supp. 5):1-51; Pohl, R.W. and G. Davidse. 1994. Enteropogon Nees.P. 289 in G. Davidse, M. Sousa S., and A.O. Chater (eds.). Flora Mesoamericana, vol. 6: Alismataceae a Cyperaceae. Universidad Nacional Autónoma de México, Instituto de Biología, México, D.F., México. 543 pp.

1	Panicles with 3-15 branches racemosely arranged; plants rhizomatous ..... 1. E. chlorideus
	Panicles with 1-10 branches in a single, digitate cluster; plants not rhizomatous, sometimes stoloniferous (2)
2	Panicle branches 6-11 cm long, erect to slightly diverging; spikelets with 5-6 florets, the distal 4-5 sterile; plants stoloniferous ..... 2. E. prieurii
	Panicle branches 7-25 cm long, divergent to drooping; spikelets with 2 florets, the distal floret sterile; plants not stoloniferous ..... 3. E. dolichostachyus

1. Enteropogon chlorideus (J. Presl) Clayton
Buryseed Umbrellagrass

Plants perennial; cespitose and rhizomatous, each rhizome terminating in a cleistogamous spikelet. Culms to 100 cm, erect. Sheaths sparsely pilose near the ligules; ligules of lower leaves with a single prominent tuft of hairs; ligules of upper leaves usually glabrous; blades to 30 cm long, to 1 cm wide, usually scabrous, occasionally pilose. Panicles with 3-10(15) racemosely arranged branches, usually most nodes with more than 1 branch; branches 6-10 cm, naked below, with about 4 spikelets per cm distally. Spikelets with 1 bisexual and 1 sterile floret. Lower glumes 1-2 mm; upper glumes 2-3.5 mm; lower lemmas 4.5-7.5 mm long, about 1 mm wide, linear to narrowly lanceolate, glabrous or the margins sparsely strigose above, apices acute to acuminate, often bidentate, unawned or awned, awns 6.5-15 mm; sterile florets 1.4-3 mm long, to 0.3 mm wide, awns 2-8 mm. Chasmogamous caryopses about 4.5 mm long, about 0.8 mm wide; cleistogamous caryopses to 4 mm long, about 2.5 mm wide. 2n = 40, 80.

Enteropogon chlorideus is native from the southwestern United States through Mexico to Honduras. The spikelet-bearing rhizomes distinguish Enteropogon from most other grasses, but they are often missing from herbarium specimens. Seed set is highest in the cleistogamous spikelets.

2. Enteropogon prieurii (Kunth) Clayton
Prieur's Umbrellagrass

Plants perennial; stoloniferous. Culms to 80 cm. Sheaths glabrous, occasionally pilose apically; ligules short ciliate to long pilose; blades 10-30 cm long, to 5 mm wide, glabrous abaxially, scabrous to pilose adaxially. Panicles with 3-7 branches in a single digitate cluster; branches 6-11 cm, erect to slightly divergent, with 8-11 spikelets per cm. Spikelets with 1 bisexual floret and 4-5 sterile florets. Lower glumes 2.1-2.2 mm; upper glumes 3.7-4 mm; lowest lemmas 3.3-4.7 mm long, 0.4-0.7 mm wide, narrowly elliptic, margins densely strigose distally; lowest sterile florets 1.5-2.5 mm, cylindrical, awned, awns 8-17 mm; distal florets about 0.3 mm, flabellate. Caryopses 2-2.5 mm long, about 0.5 mm wide. 2n = unknown.

Enteropogon prieurii is native to the tropics of the Eastern Hemisphere. It was found near wharves in Alabama and North Carolina at the beginning of the twentieth century, but it is not known to be established in the Flora region.

3. Enteropogon dolichostachyus (Lag.) Keng ex Lazarides

Plants perennial; cespitose, neither stoloniferous nor rhizomatous. Culms 75-90 cm, branched, ascending or scrambling, sometimes rooting at the lower nodes. Sheaths glabrous or pubescent, sometimes hispid on the margins, distal margin hairs stiff, 2-4 mm; ligules about 0.3 mm; blades 10-17(40) cm long, 2.8-7 mm wide, usually flat, tapering to the apices. Panicles with (1)2-4(7) branches in a single digitate cluster; branches 7-15(25) cm, divergent to drooping, spikelet-bearing to the base. Spikelets with 2 florets. Glumes hyaline to thinly membranous, lanceolate, scabrous or smooth, long-acuminate; lower glumes 1.5-3 mm; upper glumes 4-6.5 mm; lower lemmas 3.5-5 mm, scabrous distally, notched, awned, awns 7-15 mm; distal florets about 0.8-1.8 mm, sterile, attenuate into the rachilla, awned, awns 3-7 mm. Caryopses 2.5-3 mm; embryos about 1 mm. 2n=20, 40, 60.

Enteropogon dolichostachyus grows from Afghanistan through southeast Asia to Australia. It has been collected from near a woolen mill in South Carolina, but it is not known to be established in the Flora region.