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

856 POACEAE/BROMUS
ined.). A number of species are similar morphologically, hybridization is apparently common,
and polyploidy is frequent (Smith 1972). Some are used as ornamentals and a number are utilized
for forage. Other species are unpalatable, thus gaining the name CHEATGRASS, and the
sharp pointed florets and long rough awns of some can even injure the eyes, noses, mouths, and
digestive systems of livestock (Clayton & Renvoize 1986; Yatskievych 1999; Pavlick ined.). Unfortunately,
a number of species have become problematic invaders of native habitats, and in
some parts of the U.S., large areas of native grasses have been replaced by introduced members
of the genus (Yatskievych 1999); many species are considered significant weeds (Watson &
Dallwitz 1992). The awns serve to attach the fruits to animals, and it has been suggested that
the curving of the awns (which increases upon drying) promotes dispersal by mechanically
dislodging mature fruits by chance external friction (Ainouche et al. 1996). However, Peart
(1979, 1981) argued that awns serve other purposes such as moving fruits across the soil surface
to favorable microsites (in the case of awns that change shape upon drying) or orienting seeds
in a position relative to the soil surface that maximizes water uptake for germination and establishment.
The following treatment draws heavily on Yatskievych (1999). (An ancient Greek
name for oats; from broma, food) (subfamily Pooideae, tribe Bromeae)
REFERENCES: Wagnon 1952; Raven 1960; Klemmedson & Smith 1964; Soderstrom & Beaman
1968; Smith 1970, 1972, 1981; Pinto-Escobar 1976, 1981; Krzakowa & Kraupe 1981; Stebbins
1981b; Novak et al. 1991, 1993; Smith & Sales 1993; Pavlick 1995, ined.; Pillay & Hilu 1995;
Ainouche et al. 1996, 1999; Tucker 1996; Oja 1998; Oja & Jaaska 1998; Yatskievych 1999;
Planchuelo & Peterson 2000; Bartlett et al. 2002.
1. Spikelets strongly flattened; glumes and lemmas sharply keeled; lemmas awnless or with a short
awn 3.5 mm or less long _________________________________________________________ B. catharticus
1. Spikelets not strongly flattened; glumes and lemmas not sharply keeled; lemmas with awn 2–65
mm long (or in B. inermis which is rare in East TX, awnless or with an awn 3 mm or less long).
2. Lower (first) glume with only 1 vein (rarely with 2 additional veins near base); upper glume
usually with 3 veins (rarely with 2 additional faint marginal veins).
3. Plants perennial; species EITHER with well-developed rhizomes OR of wooded habitats;
awns absent or 0.5–8 mm long; leaf blades 5–10(–15) mm wide.
4. Lemmas glabrous, with awn absent or 3 mm or less long; inflorescence branches stiffly
ascending at maturity; rhizomes well-developed, creeping; plants in loose colonies, typically
found in open or disturbed areas, rare in East TX, known only from Anderson and
Robertson cos. _____________________________________________________________ B. inermis
4. Lemmas usually densely pubescent, with awn 2–8 mm long; inflorescence branches
spreading or drooping at maturity; rhizomes absent or poorly developed; plants in tufts
or clumps, typically found in wooded areas, widespread in East TX _________________ B. pubescens
3. Plants annual; species without rhizomes and usually (but not always) of open habitats;
awns 6–65 mm long; leaf blades 2–7 mm wide.
5. Spikelets large, (25–)30–40 mm long excluding awns; lemma bodies 18–30 mm long;
awn of lemmas 30–50(–65) mm long __________________________________________ B. diandrus
5. Spikelets much smaller, ca. 12–20 mm long excluding awns; lemma bodies 8–12 mm
long; awn of lemmas 6–18 mm long.
6. Awn of lemmas usually 10–18 mm long; apical teeth of lemmas often � conspicuous,
ca. 1–3(–5) mm long; species widespread in East TX, typically in open habitats ______ B. tectorum
6. Awn of lemmas 6–10 mm long; apical teeth of lemmas inconspicuous, 0–0.5 mm long;
species endemic to TX and known in East TX only from Bexar, Burleson, and Travis
cos. near sw margin of area, typically in shady habitats __________________________ B. texensis
2. Lower glume with 3–5 veins; upper glume with 5–7 veins.
7. Awn of lemmas usually 15–50(–65) mm long; spikelets large, (20–)30–50 mm long at maturity
excluding awns; species rare in East TX.