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Published In: Historia Stirpium Indigenarum Helvetiae Inchoata 2: 244. 1768. (Hist. Stirp. Helv.) Name publication detail
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/22/2009)

 

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62. Digitaria Haller (crab grass)

Plants with C4 photosynthesis, annual or perennial, forming tufts or mats. Flowering stems erect to spreading, often ascending from spreading bases, sometimes rooting at the lowermost nodes, glabrous. Leaf sheaths glabrous or hairy, keeled, the ligule a short membrane, usually with an uneven or irregularly toothed margin. Leaf blades flat, hairy or glabrous. Inflorescences of several spikelike racemes, these arranged digitately at the tip of the main inflorescence axis or nearly so, or in a panicle with a short main axis, or (in D. cognata) the inflorescence an open, highly branched panicle with individual, long‑stalked spikelets. Spikelike racemes (when present) appearing 1‑sided, with the spikelets occurring in 2 rows along 1 side of the narrowly or broadly winged axis, the axis with a spikelet at the tip. Spikelets not subtended by bristles or spines, without a cuplike ring or knoblike disk at the base. Lower glume absent or minute and triangular, often shed prior to flowering. Upper glume shorter than to about as long as the rest of the spikelet, not inflated or saclike at the base, bluntly to sharply pointed at the tip, awnless, 3‑ or 5‑nerved, glabrous or more commonly hairy. Lowermost floret sterile, the palea absent or highly reduced, the lemma about as long as the rest of the spikelet, bluntly to sharply pointed at the tip, awnless, 5‑nerved, glabrous or more commonly hairy. Fertile (perfect) floret with the lemma about as long as that of the staminate or sterile floret, bluntly to sharply pointed at the tip, awnless, nerveless or very faintly 3‑nerved, glabrous, dull, somewhat thickened and leathery (not bonelike), but with thinner, lighter‑colored, relatively flat margins, often only slightly wrapped around the palea and fruit. Paleas glabrous, dull, somewhat thickened and leathery, but with thinner margins. Fruits oblong‑elliptic in outline, white to brown. About 220 species, nearly worldwide, mostly in tropical and subtropical regions.

A number of species of Digitaria are important as weeds of lawns, crop fields, and grassland communities.

 

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1 Inflorescence an open, highly branched panicle; spikelets with stalks 10–40 mm long, not grouped on 1 side of the unwinged axis of the branch 2 Digitaria cognata
+ Inflorescence of several spikelike racemes, these arranged digitately at the tip of the main inflorescence axis or nearly so, or in a panicle with a short main axis; spikelets with stalks 0.5–3.0 mm long, grouped in 2 rows on 1 side of the narrowly to broadly winged axis of the spikelike raceme (2)
2 (1) Florets mostly replaced by vegetative bulblets 4 Digitaria ischaemum
+ Florets not replaced by vegetative bulblets, the plants with all “normal” spikelets (3)
3 (2) Axis of the spikelike racemes very narrowly winged, the wings narrower than the midrib of the axis 3 Digitaria filiformis
+ Axis of the spikelike racemes more broadly winged, the wings as wide as or wider than the midrib of the axis (4)
4 (3) Spikelets 1.7–2.3 mm long, the upper glume about as long as the rest of the spikelet; leaf sheaths glabrous or with sparse hairs along the margins near the tip 4 Digitaria ischaemum
+ Spikelets 2.4–3.6 mm long, the second glume 1/3–3/4 as long as the rest of the spikelet; leaf sheaths hairy on the surface and margins (5)
5 (4) Leaf blades glabrous or sparsely hairy on the upper surface near the base; sterile floret with the lateral nerves of the lemma glabrous (there may be minute hairs or a few longer hairs between the nerves, especially near the margins) 1 Digitaria ciliaris
+ Leaf blades moderately to densely hairy on both surfaces; sterile floret with the lateral nerves of the lemma roughened with minute, stiff teeth (sometimes also hairy between the nerves or especially near the margins) 5 Digitaria sanguinalis
 
 
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