Belongs within: Paniceae.
Digitaria, the crabgrasses, is a genus of grasses producing long, finger-like inflorescences. Fonio D. exilis and D. ibarua are grown as grain crops in parts of Africa (Kellogg 2015). Smooth crabgrass D. ischaemum is regarded as a lawn and garden weed in North America. It is characterised by smooth leaves, generally three spikelets per node, and lower glumes that are a translucent scale or absent. The Australian D. brownii has densely hairy spikelets with an indumentum of soft, woolly hairs much exceeding the spikelet (Gardner 1952).
Characters (Gardner 1952): Perennials or annuals; leaf-blade linear to linear-lanceolate, usually flat, often more or less flaccid; ligule membranous; inflorescence a number of spike-like racemes on a common axis; racemes sessile, digitate and usually distant, sometimes bare at base owing to arrest of spikelets, rarely truly peduncled, simple or sometimes compound near base; rhachis triquetrous, with narrow green margins or herbaceous wings on lateral angles, or flattened with terete midrib. Spikelets solitary or usually two or three together, more rarely 4–6-nate, secund and abaxial (back of lower glume and sterile lemma turned away from axis), pedicelled, lanceolate to elliptical-oblong in outline, flat or more or less concave in front, convex on back, closely appressed to rhachis and more or less imbricate, or lax, usually silky though often apparently glabrous, rarely quite glabrous, falling entire; pedicels unequal. Floret 1. Glumes very dissimilar, the lower a minute membranous scale or very delicate readily disintegrating hyaline membrane, sometimes quite suppressed; upper membranous, sometimes very thin, appressed to back of upper lemma, 5- (or more often 3-)nerved, very rarely 1-nerved or almost nerveless, sometimes quite suppressed. Lemmas 2, the lower sometimes resembling upper glume, but generally larger and as large as fertile lemma, 7–8-nerved or very rarely 3-nerved with nerves parallel and prominent if not obscured by hairs, rarely reduced to small scale, not subtending a floret; upper (fertile) lemma chartaceous or almost so, with thin hyaline margins, faintly 3-nerved, subtending bisexual floret. Paleas 2, the lower minute, the upper equal or subequal to fertile lemma and embraced by it throughout its length, finely 2-nerved. Lodicules 2, broadly cuneate. Stamens 3. Styles distinct; stigmas laterally exserted near tip of spikelet. Grain tightly embraced by slightly hardened lemma and palea, oblong, more or less dorsally compressed, plano-convex in cross-section with rounded sides; hilum basal, punctiform; embryo less than half length of grain.
Digitaria Haller 1768K15
|--D. adscendens (H.B.K.) Henr. 1934 [=Panicum adscendens]G52
|--D. albudensS03
|--D. ammophila (Muell.) Hughes 1923 [=Panicum divaricatissimum var. ammophilum]G52
|--D. bicornisLK14
|--D. brownii (R. & S.) Hughes 1923G52 (see below for synonymy)
| |--D. b. var. browniiG52
| `--D. b. var. monostachyaG52
|--D. catamarcensisK15
|--D. coenicola (Muell.) Hughes 1923G52 [=Panicum coenicolum Muell. 1855G52, B78]
|--D. cruciata [=Panicum cruciatum]KYK07
|--D. ctenantha (Muell.) Hughes 1923 [=Panicum ctenanthum]G52
|--D. didactylaB00
|--D. erianthaG52
| |--D. e. var. erianthaG52
| `--D. e. var. paspaloidesG52
|--D. exilisK15
|--D. filiformisV72
|--D. gibbosaLK14
|--D. glaucaWM20
|--D. griffithiiS03
|--D. humifusaC55
|--D. iburuaK15
|--D. ischaemumRJ11
|--D. longiflora (Retz.) Pers. 1805G52 (see below for synonymy)
| |--D. l. var. longifloraB78
| `--‘Paspalum brevifolium’ var. propinquum [=Panicum propinquum]B78
|--D. mariannensisLK14
|--D. nematostachyaLK14
|--D. papposaLK14
|--D. pennataPP07
|--D. radicosaLK14
|--D. setigeraVB02
|--D. stenostachyaLK14
|--D. strictaKYK07
|--D. tomentosum (Koenig) Henrard 1934 [=Milium tomentosum Koenig ex Willdenow 1803; incl. Panicum subeglume Trin. 1834]SR07
`--D. wallichianaS03
Digitaria brownii (R. & S.) Hughes 1923G52 [=Panicum browniiG52; incl. P. glareaeB78, P. laniflorumB78, P. leucophaemG52, P. villosumB78]
Digitaria longiflora (Retz.) Pers. 1805G52 [=Paspalum longiflorumG52; incl. Pas. brevifoliumG52, Panicum steudelianumG52, Pan. tenuiflorumB78, Digitaria tenuifloraG52]
*Type species of generic name indicated
References
[B78] Bentham, G. 1878. Flora Australiensis: A description of the plants of the Australian Territory vol. 7. Roxburghiaceae to Filices. L. Reeve & Co.: London.
[B00] Braby, M. F. 2000. Butterflies of Australia: their identification, biology and distribution vol. 2. CSIRO Publishing: Collingwood (Victoria).
[C55] Candolle, A. de. 1855. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 2. Librairie de Victor Masson: Paris.
[G52] Gardner, C. A. 1952. Flora of Western Australia vol. 1 pt 1. Gramineae. William H. Wyatt: Perth.
[K15] Kellogg, E. A. 2015. The Families and Genera of Vascular Plants vol. 13. Flowering Plants: Monocots: Poaceae. Springer.
[KYK07] Khan, M. R., P. S. Yadava & A. Kikim. 2007. Additions to the flora of Manipur. Bulletin of the Botanical Survey of India 49: 215–218.
[LK14] Lyons, M. N., G. J. Keighery, L. A. Gibson & T. Handasyde. 2014. Flora and vegetation communities of selected islands off the Kimberley coast of Western Australia. Records of the Western Australian Museum Supplement 81: 205–244.
[PP07] Pandey, R. P., & P. M. Padhye. 2007. Studies on phytodiversity of Arid Machia Safari Park-Kailana in Jodhpur (Rajasthan). Bulletin of the Botanical Survey of India 49: 15–78.
[RJ11] Rising, J. D., A. Jaramillo, J. L. Copete, P. G. Ryan & S. C. Madge. 2011. Family Emberizidae (buntings and New World sparrows). In: Hoyo, J. del, A. Elliott & D. A. Christie (eds) Handbook of the Birds of the World vol. 16. Tanagers to New World Blackbirds pp. 428–683. Lynx Edicions: Barcelona.
[SR07] Sankar, R. V., K. Ravikumar, N. M. Ganesh Babu & D. K. Ved. 2007. Botany of Anapady MPCA, Palghat district, Kerala with special emphasis on species of conservation concern. Bulletin of the Botanical Survey of India 49: 165–172.
[S03] Singh, J. N. 2003. Grasses and their hydro-edaphic characteristics in the grassland habitat of Nilgiris Biosphere Reserve, Tamil Nadu. Bulletin of the Botanical Survey of India 45: 143–164.
[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.
[V72] Voss, E. G. 1972. Michigan Flora. Part I. Gymnosperms and Monocots. Cranbrook Institute of Science and University of Michigan Herbarium.
[WM20] Welker, C. A. D., M. R. McKain, M. C. Estep, R. S. Pasquet, G. Chipabika, B. Pallangyo & E. A. Kellogg. 2020. Phylogenomics enables biogeographic analysis and a new subtribal classification of Andropogoneae (Poaceae—Panicoideae). Journal of Systematics and Evolution 58 (6): 1003–1030.