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

POA/POACEAE 1035
around awn base; lemma base and rachilla together forming a sharp-pointed bearded callus;
palea slightly longer than the lemma, longitudinally grooved, the apex protruding between the
lemma margins; caryopsis permanently enclosed within the lemma. Woodlands in shade, forest
margins, sandy soils; widespread in Pineywoods and Post Oak Savannah w to Limestone,
Robertson (BRIT), and Van Zandt (Turner et al. 2003) cos.; also n Gulf Prairies and Marshes and
e Edwards Plateau; se Canada (Ont.) and e U.S. from MA s to FL w to MI and TX. Mar–Jun. [Stipa
avenacea L.] This species can be confused with Nassella leucotricha (TEXAS WINTER GRASS), but
can be distinguished by habitat (Nassella in open disturbed sites) by the lemmas (Nassella with
lemmas light brown, with overlapping margins, and apically with a smooth white neck ca. 0.6–
1 mm long), and by the ligules (Nassella with ligules 1 mm or less long).
POA L. BLUE GRASS
Annuals or perennials, sometimes with rhizomes; ligule a membrane; leaf blades sometimes
with tips cupped; inflorescences open or contracted panicles; spikelets relatively small, usually
with 2–6(–10) florets, awnless, disarticulating above glumes and between florets; glumes
shorter than rest of spikelet; lemmas acute or obtuse, usually keeled on back, often with long,
kinky hairs at base.
AA C3 genus of ca. 575 species, Poa is the largest genus of grasses (Gillespie & Soreng 2005). It
is widespread but principally of temperate and cold areas of the world, including tropical
mountains. Some are important as fodder grasses and for use in lawns and playing fields; many
are important as pasture species, while a number are significant weeds (Watson & Dallwitz
1992). The genus approaches Festuca (lemmas rounded on back), but differs in its keeled lemma
(Clayton & Renvoize 1986). Poa is morphologically rather uniform (Clayton & Renvoize 1986),
and there is apparently little agreement on subdivisions within the genus (Tucker 1996). However,
recent molecular research (e.g., Gillespie & Soreng 2005) has begun to clarify the broad
phylogenetic structure within the genus. It is a taxonomically difficult group because of the
widespread occurrence of polyploidy, apomixis, hybridization, and introgression (Clayton &
Renvoize 1986; Soreng & Kellogg ined.). Some of the species have variable numbers of chromosomes,
including aneuploid series (Tucker 1996). (Greek: poa, ancient name for grass or fodder)
(subfamily Pooideae, tribe Poeae)
REFERENCES: Marsh 1952; Hutchinson & Seymour 1982; Soreng 1990, 1998; Tucker 1996; Soreng
& Barrie 1999; Soreng & Kellogg ined; Gillespie & Soreng 2005.
1. Florets developing into bulbils (often dark purple at base), the lemmas prolonged to 5–15 mm
long as if sprouting; culms swollen at base; rare in TX, known only from Denton Co. near w margin
of East TX _____________________________________________________________________ P. bulbosa
1. Florets not developing into bulbils; culms not swollen at base; including species widespread
and abundant in East TX.
2. Plants annual, 3–45 cm tall, without rhizomes; keel of glumes smooth (P. annua) or minutely
scabrous-ciliate (P. bigelovii and P. chapmaniana).
3. Branches of inflorescence appressed-erect, the inflorescence thus narrow and contracted,
usually � 1 cm wide; species known in East TX only from Travis Co. on extreme w margin of
area _______________________________________________________________________ P. bigelovii
3. Branches of inflorescence spreading (at least the lower ones), the inflorescence thus not
narrow, usually � 1 cm wide; including species widespread in East TX.
4. Lemmas with long, kinky, cobwebby hairs at base, with 3 strong and 2 faint veins; anthers
0.1–0.3 mm long; species rare in East TX ________________________________ P. chapmaniana
4. Lemmas usually without long hairs at base (but long-pubescent on margins and keel),
with 5 strong veins; anthers 0.5–1.3 mm long; species widespread and abundant in East
TX ________________________________________________________________________ P. annua