The grass genera of the world
Habit, vegetative morphology. Small annual; caespitose. Culms 15 cm high; herbaceous. Young shoots extravaginal. Leaf blades narrow; without abaxial multicellular glands; without cross venation. Ligule a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a single spike (cylindrical); non-digitate. Rachides hollowed and winged. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating; disarticulating at the joints. Articles non-linear (hollowed to receive the spikelets); appendaged (with small, lateral auriculate wings). Spikelets solitary; not secund; alternately distichous; sessile.
Female-fertile spikelets. Spikelets small; adaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret.
Glumes one per spikelet (the G2); (the G2) exceeding the spikelets (covering the sunken floret); long relative to the adjacent lemmas (shorter than the joint); not pointed (obtuse); awnless; non-carinate. Upper glume (i.e. the only one) 5 nerved, or 7 nerved (?). Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (scarious); not becoming indurated; entire; pointed, or blunt; awnless; the nerves ciliate; without a germination flap; 3 nerved. Palea present; not indurated (scarious); 2-nerved. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (about 2 mm long). Hilum short. Pericarp free. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; nearly all intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell, or several per cell (mostly large, thick walled, more or less symmetrical). Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity irregular, coarse). Microhairs present; more or less spherical; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 12 microns long. Microhair total length/width at septum 1.6. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries non-papillate; dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs to not paired; silicified. Intercostal silica bodies imperfectly developed; tall-and-narrow to acutely-angled. Prickles present, confined to the midrib. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; present in alternate cell files of the costal zones; saddle shaped.
Transverse section of leaf blade, physiology. Leaf blades consisting of midrib to laminar (largely dominated by the midrib, with only 2–3 bundles in each small lateral flange, in the material seen). Lamina mid-zone in transverse section open.
C4. The anatomical organization conventional. XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Midrib conspicuous; having a conventional arc of bundles (a large median primary, a smaller primary on either side, and 2–3 minor bundles in between); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms represented only by a pair of large midrib hinges. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (in the lamina bundles, but the fibre groups scanty). Sclerenchyma all associated with vascular bundles. The lamina margins without fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): cf. Chloridoideae (as a synonym?); Cynodonteae; Eleusininae. 1 species (I. pulchellus).
Distribution, phytogeography, ecology. Socotra.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us.
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’.