The grass genera of the world
Habit, vegetative morphology. Perennial; decumbent. Culms about 20–100 cm high; herbaceous. Leaves not basally aggregated; non-auriculate. Leaf blades broadly linear (and acuminate); broad to narrow; to 15 mm wide; flat; without cross venation; persistent. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and female-only, or male-only (sessile hermaphrodite, pedicelled male or sterile?); overtly heteromorphic (the pedicelled spikelet larger, glabrous, asymmetrically winged via the G1, awnless).
Inflorescence. Inflorescence a single raceme; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes racemes (with many spikelets); solitary; with substantial rachides; disarticulating; disarticulating at the joints. Articles non-linear (more or less clavate); ciliate. Spikelets paired; sessile and pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets (the sessile members, to which this description is confined) 5–8 mm long; compressed laterally (compressed between the internode and the pedicel); falling with the glumes. Rachilla terminated by a female-fertile floret.
Glumes two; long relative to the adjacent lemmas; awnless (G1 bidentate, G2 muticous or mucronate); very dissimilar (G1 2-keeled and grooved, G2 naviculate with a winged crest above). Lower glume two-keeled; sulcate on the back (the keels closely apposed). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male. The proximal lemmas awnless.
Female-fertile florets 1. Lemmas incised; deeply cleft (bifid to 3/4 of their length); awned. Awns 1; median; from a sinus; geniculate; hairless (glabrous); much longer than the body of the lemma (8–15 mm long). Lemmas hairless; non-carinate; without a germination flap.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 42–45.6–48 microns long; 4.8–6–7.5 microns wide at the septum. Microhair total length/width at septum 5.6–7.7–9.4. Microhair apical cells 12–16.8–21 microns long. Microhair apical cell/total length ratio 0.29–0.37–0.44. Stomata common; 24–30 microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells fairly common; not paired (solitary). Exhibiting abundant, short-tipped prickles with almost spherical bases, and large macrohairs with conspicuous basal rosettes. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies absent to poorly developed; (these, or at least the silica cells) panicoid-type; nodular.
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath outlines even. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Midrib having a conventional arc of bundles (one large median, and several small ones on either side, nearer the abaxial surface); with colourless mesophyll adaxially (the large adaxial colourless mass more or less lignified, and merging into fibre groups adaxial to the median bundle and beneath the adaxial epidermis). The lamina symmetrical on either side of the midrib. Bulliforms not present in discrete, regular adaxial groups (for the most part - the epidermis extensively bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (but only in a few of the main bundles - the rest with strands only). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Ischaeminae. 1 species (A. stolzii).
Distribution, phytogeography, ecology. Tropical Africa.
Mesophytic. Forest margins.
References, etc. Leaf anatomical: studied by us.
Special comments. Note that spikelet details are given here only for the sessile spikelet. Fruit data wanting. Illustrations. • A. stolzii, as A. variegatum: Hook. Ic. Pl. 31 (1922)
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 11th December 2017. delta-intkey.com/grass’.