Compilation
Digitaria boivinii

A variable species, being usually loosely tufted and rhizomatous, but with forms ranging from geniculate or stoloniferous to erect and caespitose. A number of indistinct variants may be recognized, the principal being:1. D. milanjiana. Spikelets sparsely hairy with scabrid nerves; sheaths mostly glabrous; nodes glabrous. The scabrid nerves distinguish it from other East African species, but this is not an easy character to see; it is often easier to recognize the long (8–25 cm.) stiff subdigitate racemes of inconspicuously hairy spikelets.2. D. setivalva. Nerves of the upper lemma bearing stiff glassy bristles. In all other respects the range of variation, geographical distribution and frequency is matched by D. milanjiana, and the distinction seems to be rather artificial. It is often difficult to see the scabridity of the nerves among the bristles, and it might be confused with D. macroblephara which sometimes has a few hairs; the villous spikelets and bushy habit of the latter help to distinguish it.3. D. mombasana. Leaf sheaths villous; nodes glabrous or pilose; spikelets with or without bristles. This minor variant is commonest in coastal districts, but there are all degrees of intermediate hairiness and it is difficult to define its limits precisely.4. D. endlichii. Racemes short (5–11 cm.); plants small (up to 60 cm.); nodes glabrous or pilose; spikelets nearly always bristly. Occurs in scattered localities throughout East Africa and Zambia. An ill-defined entity representing a downward extension of raceme length and a tendency to pilose nodes, which is not matched by plants with bristleless spikelets; it intergrades so completely with D. setivalva that it is impractical to attempt its segregation.The scabrid nerves separate D. milanjiana from its allies in South Africa. The distinction is perhaps arbitrary, but at least it serves to isolate the strictly tropical element. The southern species are intergrading and imperfectly defined, the commonest being D. eriantha Steud. (caespitose) and D. pentzii Stent (stoloniferous). A particularly rampant form (apparently the progeny of 2 or 3 plants selected from the wild) of the latter with almost glabrous spikelets has been extensively grown for fodder under the name of D. decumbens Stent or Pangola grass. D. swazilandensis Stent is another member of the complex. It is a mat-forming perennial with slender creeping stolons; racemes 2–5, each 3–9 cm. long; spikelets 1.7–2.5 cm. long, indistinctly pubescent; upper glume 1/3–2/3 as long as the spikelet. A native of South Africa, it intergrades with the more robust D. pentzii; and also with D. seriata Stapf (hairier spikelets, the upper glume 1/2–2/3 as long) from Zimbabwe and its neighbours. It has been introduced to East Africa as a lawn grass. It is difficult to distinguish from D. didactyla Willd., a more delicate trailing perennial with 2–3 racemes up to 6 cm. long and the upper glume 1/2–3/4 as long as the spikelet. D. didactyla is a native of the Mascarene Islands, and has been introduced to several tropical countries as a lawn grass under the name Blue Couch.