Syntherisma glabra Schrad.
Annual; culms (10-)1540 cm high, erect or geniculately ascending. Leaf-blades 2.5-11 cm long, 3.5-8 mm wide. Inflorescence composed of 2-4(-6) racemes; racemes 2.5-8(11) cm long, subdigitate or arranged along an axis 1.5-2(4) cm long, the spikelets ternate on a ribbon-like winged rhachis with rounded or triquetrous midrib; pedicels terete to flattened and winged, scabrid, with discoid or cupuliform tip. Spikelets elliptic or lanceolate, 1.9-2.4 mm long; lower glume an obscure hyaline rim; upper glume almost as long as the spikelet, 5-nerved, with matted verrucose hairs between the nerves; lower lemma as long as the spikelet, 7-nerved, pubescent with matted verrucose hairs; fruit ellipsoid, dark brown to almost black.
Fl. & Fr. Per.: July-August.
Type locality: Germany.
Distribution: Pakistan (N.W.F.P., Gilgit & Kashmir); North America; Europe extending eastwards into northern Asia.
Other, unlocalised, records are Kashmir, J.L. Stewart 850b(K) and Gilgit, R.R. Stewart 26652(K).
Digitaria ischaemum is much more closely related to Digitaria violascens than has hitherto been supposed. Henrard placed it in his section Clavipilae, along with Digitaria stricta, but close examination of the hairs has shown that they are not in fact clavate Although they appear, under moderate magnification, to have a clavate tip, this is not due to a swelling, but to a curious crozier-like curling of the tip of the hair itself. Furthermore, when viewed under higher magnification (preferably through a compound microscope), the hairs can be seen to be verrucose. Apart from geographical distribution, the main distinctions between Digitaria ischaemum and Digitaria violascens lie in the larger spikelets of Digitaria ischaemum and its longer, matted, pseudo-clavate hairs.