keys to the vascular plants of east texas - Botanical Research ...

ARISTIDA/POACEAE
829
9. Lemma thick to base of awns (from 0.2 to 0.8 mm wide); awn column absent.
10. Awns 4–10+ cm long ___________________________________ A. purpurea var. longiseta
10. Awns 3.5 cm or less long.
11. Plants annual, often much-branched basally, but base neither knotty nor
thickened; leaf blades usually 0.5–1 mm wide; glumes about equal; central
awn (1–)5–27(–36) mm long; lemma 2.5–10 mm long; lateral awns
sometimes reduced and 1/2 or less the length of the central awn OR welldeveloped
___________________________________________________ A. longespica
11. Plants perennial, from a knotty thickened base; leaf blades usually 1–3 mm
wide (however, they can be involute and thus appear narrower); glumes
about equal OR lower glume half to three-fourths as long as upper; central
awn 15–40 mm long; lemma 5–15.5 mm long; lateral awns well-developed,
at least 1/2 the length of the central awn.
12. Lemma 11–15.5 mm long (to base of awns); lower glume 1/2–3/4 as
long as the upper glume; species of dry calcareous habitats, known in
East TX only from the Blackland Prairie ________________ A. purpurea var. wrightii
12. Lemma 5–9.2 mm long; lower glume slightly shorter to longer than
the upper glume; species of sandy or moist habitats, widespread in
East TX.
13. Upper glume 5–8 mm long; lower glume 1-keeled (1–2 veined,
but if 2-veined without a flat area between the keel and the second
vein); anthers 1–1.5 mm long; species widespread in East TX
__________________________________________________ A. purpurascens
13. Upper glume (7.5–)9–13.5 mm long; lower glume prominently 2keeled
(with a flat area between the 2 keels/veins); anthers ca. 3
mm long; species known in East TX only from Hardin, Newton,
and Tyler cos. in the s part of the Pineywoods __________________ A. palustris
Aristida basiramea Engelm. ex Vasey, (branching from base), FORK-TIP THREEAWN, FORKED
THREEAWN. Annual to 45 cm tall; panicles contracted; glumes about equal, to 12 mm long including
awn; lemma 8–9 mm long, the central awn 9–15 mm long, conspicuously spirally
coiled, the lateral awns spreading, 4–10 mm long. Sandy soils; Dallas (BRIT), Bastrop, and Red
River (Gould 1975b) cos., apparently known in TX only from these three counties (Gould
1975b); se Canada (Ont.) and c U.S., scattered further e. Aug–Oct. According to Allred (1986), this
species is similar to A. dichotoma and could be treated as a variety of that species. The two are
distinguished by A. basiramea having spreading lateral awns usually 4–10 mm long (vs. lateral
awns erect, 1–2 mm long in A. dichotoma). While not officially designated as such (e.g., TOES
1993; Carr 2002d; Poole et al. 2002), given its limited distribution in the state, we consider this
species to be of conservation concern in TX. �
Aristida desmantha Trin. & Rupr., (with clustered flowers), CURLY THREEAWN, WESTERN
TRIPLEAWN, WESTERN THREEAWN, SAND THREEAWN. Annual; leaf sheaths glabrous to lanate pubescent;
panicles loosely contracted, 8–20 cm long; spikelets light yellowish or golden-brown;
glumes 1-veined, awn-tipped, about equal, 10–17 mm long (including awn); lemma 7–10 mm long,
the awns about equal, 2–3(–3.5) cm long, spreading; awn column jointed basally, well-defined.
Sandy soils; widespread in e 1/2 of TX; also Trans-Pecos; AR, IL, LA, MO, NE, OK, and TX. Sep–Nov.
Aristida dichotoma Michx., (2-parted or forked), CHURCH-MOUSE THREEAWN, POVERTY GRASS, PIG-
BUTT THREEAWN. Annual 15–60(–75) cm tall; inflorescence a contracted panicle or spike-like
raceme; glumes about equal or the upper glume longer; lemma 4–6 mm long, rarely longer;
central lemma awn 3–8 mm long, spirally coiled basally; lateral lemma awns 1–2(–4) mm long,
erect. Sandy soils; Bastrop, Dallas, Grayson, Lamar (BRIT), Bowie, Brazos, Freestone, Red River,
St. Augustine, and Travis (Turner et al. 2003) cos.; also e Edwards Plateau and Brazoria Co.