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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 6/2/2011)
Acceptance : Accepted
Project Data     (Last Modified On 6/3/2011)
General/Distribution: A genus of about 200 species in tropical and warm temperate regions, particularly in the Old World; 14 species occur in Pakistan, 2 of them in cultivation only, 1 an alien weed.
Comment/Acknowledgements: Digitaria is not an easy genus to name. It is traditionally subdivided according to the nature of the hairs, but this requires a microscope, and the different kinds of hair form a continuous spectrum rather than discrete groups, with a sprinkling of glabrous variants to complicate the situation. Reliance is here placed early on in the key upon spikelet grouping. This works reasonably well, but is sometimes deceptive. Ternate spikelets often have the longest pedicel fused to the rhachis, so that the spikelets seem to be alternately solitary and paired; sometimes one of the spikelets is vestigial. Binate spikelets are often associated with the development of secondary branching, which can be misleading; in particular the pedicel is sometimes forked so that the spikelets appear ternate, but the pedicels of truly ternate spikelets all arise from the same node.

 

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Annuals or perennials. Leaf-blades mostly linear and flat; ligule short, scarious or membranous, glabrous or ciliate. Inflorescence composed of racemes, these digitate or borne upon an elongated central axis, rarely solitary, sometimes with secondary branchlets; rhachis flat or triquetrous, bearing the spikelets in appressed groups of 1-5 or more, their lower glume abaxial; pedicels terete or triquetrous, usually smooth or scaberulous. Spikelets lanceolate to oblong-elliptic, flattened on the front, convex on the back; lower glume small or suppressed; upper glume membranous, as long as the spikelet, or much shorter and exposing the upper lemma; lower floret barren, represented by a prominently nerved membranous lemma as long as the spikelet (rarely much reduced), usually hairy, typically with the hairs forming stripes between the 1st and 2nd lateral nerves and along the margin; upper floret bisexual, the lemma chartaceous to cartilaginous, finely longitudinally striate, with its hyaline margins enfolding and concealing most of the plea, ± dorsally compressed, usually rounded on the back, subacute to acuminate, rarely rostrate; caryopsis oblong, plano-convex in section, mostly acute to subacute.
 

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1.Racemes scattered along an elongated axis longer than themselves
Digitaria californica
1.Racemes digitate or subdigitate, or on a short main axis shorter than themselves
2.Spikelets ternate
3.Spikelets glabrous
Digitaria stewartiana
3.Spikelets hairy
4.Hairs on spikelets verrucose
5.Spikelets 1.9-2.4 mm long with long matted hairs curled at the tips and appearing, at low magnification, as though they are clavate
Digitaria ischaemum
5.Spikelets 1.2-2 mm long with short spreading or ± appressed hairs
6.Racemes typically 3 or more: pedicels sometimes ± flattened and winged, scabrid; upper glume noticeably shorter than the spikelet, commonly 3-nerved; fruit dark brown to almost black
Digitaria violascens
6.Racemes typically 2; pedicels terete, smooth; upper glume as long as the spikelet, 5-nerved; fruit pallid, light brown or light grey
Digitaria longiflora
4.Hairs on spikelets distinctly clavate at the tip, not verrucose
7.Tip of pedicel with a corona of hairs up to 1 mm long
Digitaria stricta
7.Tip of pedicel glabrous, without a corona
Digitaria abludens
2.Spikelets binate
8.Rhachis bare of spikelets in the lower half, pennately hairy
Digitaria pennata
8.Rhachis spiculate to the base, not pennately hairy
9.Margins of rhachis smooth
Digitaria radicosa
9.Margins of rhachis scabrid
10.Lower glume absent or very obscure
Digitaria setigera
10.Lower glume present and ± conspicuous
11.Culms with bulbous swellings at the base, the basal sheaths silky hairy
12.Racemes ± loose; rhachis winged; upper glume two thirds to as long as the spikelet; wild grass
Digitaria nodosa
12.Racemes tighter, rhachis wingless; upper glume shorter: in cultivation only
Digitaria eriantha
11.Culms not swollen at the base and without silky hairy basal sheaths
13.Nerves of lemma smooth
Digitaria ciliaris
13.Nerves of lemma with sparse to numerous minute siliceous spines or scabridities
Digitaria sanguinalis
 

Lower Taxa
 
 
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