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

910 POACEAE/DIGITARIA
subsessile, the other short-pedicelled), 2-flowered, the lower floret staminate or neuter, the upper
floret fertile; disarticulation below glumes; lower glume minute or absent; upper glume
well-developed but usually shorter than lemmas; lemma of lower floret resembling a glume;
lemma of fertile floret with margins thin and flat, not inrolled; stamens 3.
AA C4 genus of ca. 200 species of tropical to warm temperate areas of the world (Wipff 2003f).
Many species are weedy, a number are important pasture grasses, and some are cultivated for food
(grain) in Africa. As treated here, Digitaria includes Leptoloma (e.g., D. cognata), whose inflorescence
appears quite different; see that species for discussion. Three East TX species (D. californica,
D. insularis, and D. patens) were treated in the genus Trichachne by Correll and Johnston (1970).
� Digitaria velutina (Forssk.) Beauv., VELVET CARPET GRASS, a federal noxious weed, was erroneously
reported for TX by Kartesz (1999) (Wipff 2003f). (Latin: digitus, finger, from the finger-like
arrangement of the inflorescence branches) (subfamily Panicoideae, tribe Paniceae)
REFERENCES: Henrard 1950; Ebinger 1962; Gould 1963; Veldkamp 1973; Webster & Hatch 1981a,
1981b, 1983, 1990; Webster & Shaw 1982; Webster 1987, 1988; Wipff & Hatch 1988, 1994; Crins
1991; Wipff 2001b, 2003f.
1. Spikelets long-pedicelled (pedicels 2–many times as long as spikelet); inflorescence a muchbranched
and rebranched, open panicle with spikelets far apart ____________________________ D. cognata
1. Spikelets subsessile or on short, appressed pedicels; inflorescence of few to numerous, unbranched,
spike-like branches (these digitately arranged or along a short axis), the spikelets close together.
2. Inflorescence branches winged (wings often as wide as central part of branch); spikelets glabrous
to short-pubescent.
3. Spikelets 1.2–2.3 mm long; lemma of fertile floret dark brown to purplish black at maturity.
4. Spikelets (1.7–)1.9–2.3 mm long ___________________________________________ D. ischaemum
4. Spikelets 1.2–1.7 mm long _________________________________________________ D. violascens
3. Spikelets 2.2–3.7 mm long; lemma of fertile floret light brown or grayish.
5. Lemma of lower floret (lemma appearing glume-like because of minute or absent lower
glume) of the nearly sessile spikelets with the 7 (sometimes apparently 5) veins � equally
spaced, often but not always densely villous marginally (note that spikelets are in pairs,
one pedicelled and one nearly sessile); lower glume of nearly sessile spikelets rounded
to truncate or bifid, usually 0.1–0.3 mm long _____________________________________ D. bicornis
5. Lemma of lower floret of the nearly sessile spikelets with the 7 (sometimes apparently
5) veins not equally spaced, the lateral ones crowded at margins, glabrous or inconspicuously
pubescent marginally; lower glume of nearly sessile spikelets obtuse or acute,
often more than 0.3 mm long.
6. Spikelets 2.2–3.3 mm long; upper glume 0.8–1.8 mm long; leaf blades usually densely
pubescent, usually on both surfaces; lemma of lower floret minutely scabrous on
lateral veins (as seen under a dissecting scope) _____________________________ D. sanguinalis
6. Spikelets 2.8–4.1 mm long; upper glume 1.5–2.7 mm long; leaf blades glabrous or
sparsely pubescent, any hairs usually on upper surface only; lemma of lower floret
smooth on lateral veins _____________________________________________________ D. ciliaris
2. Inflorescence branches not winged or only minutely so; spikelets silky-pubescent with long
white-, tan-, buff-, or purplish-silky hairs OR not so.
7. Spikelets silky-pubescent, the inflorescences appearing conspicuously white-, tan-, buff-,
or purplish-silky-pubescent at arm’s length; spikelets 3–5.9 mm long.
8. Back of lemma of lower, sterile floret usually with pubescence or apparently so (in addition
to being conspicuously hirsute marginally); inflorescence usually tan- or buff-tinged
due to conspicuous pubescence on spikelets ____________________________________ D. insularis
8. Back (outer surface) of lemma of lower, sterile floret (lemma glume-like because of minute
1st glume) glabrous at least in a broad lengthwise band down the middle (but marginally
densely hirsute); inflorescence usually white- or purplish-tinged due to conspicuous
pubescence on spikelets.