The grass genera of the world
Type species: H. gracilis Auquier.
Habit, vegetative morphology. Slender annual. Culms 4–12(–17) cm high; herbaceous; branched above. Leaves not basally aggregated; non-auriculate. Leaf blades linear-lanceolate; narrow; 2–5 mm wide; flat, or rolled (convolute when dry); without abaxial multicellular glands; pseudopetiolate (the base very abruptly contracted); without cross venation. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants seemingly inbreeding; exposed-cleistogamous, or chasmogamous (?).
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund, or not secund.
Female-fertile spikelets. Spikelets 1.2–1.4 mm long; fusiform; somewhat compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (minute). Callus short; blunt.
Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; hairless; glabrous to scabrous; pointed (the upper being acute), or not pointed (the lower being obtuse-erose); awnless; carinate (the upper), or non-carinate (the lower); slightly dissimilar. Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (hyaline-membranous); not becoming indurated; entire; blunt (truncate); awned. Awns 1; median; apical; non-geniculate; flexuous; hairless (scaberulous); much longer than the body of the lemma; entered by one vein. Lemmas hairy (on the margins); non-carinate (dorsally rounded); 1 nerved. Palea absent. Lodicules absent. Stamens 3. Anthers 0.3–0.4 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (0.9–1 mm long); fusiform; not noticeably compressed (almost cylindrical). Hilum short. Pericarp fused. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation fairly conspicuous. Papillae present; very abundant, costal and intercostal. Intercostal papillae several per cell (nearly every cell with one or two rows of smallish, round or branch-paired papillae). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (rather thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse). Microhairs present; elongated; 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 3. Microhair apical cell/total length ratio 0.33. Stomata absent or very rare. Intercostal short-cells absent or very rare; not paired. Intercostal silica bodies absent. No macrohairs or prickles seen. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; present in alternate cell files of the costal zones; panicoid-type; cross shaped, butterfly shaped, and dumb-bell shaped (mostly dumb-bells).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; not traversed by colourless columns. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (round topped, one per bundle). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in every furrow); in simple fans (deeply penetrating). All the vascular bundles accompanied by sclerenchyma. Sclerenchyma all associated with vascular bundles (scanty). The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 1 species (H. gracilis Auquier).
Distribution, phytogeography, ecology. Rwanda, Burundi, Zambia.
Species of open habitats. Stony slopes, in savanna.
References, etc. Morphological/taxonomic: Auquier (1980). Leaf anatomical: this project.
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: 13th November 2017. delta-intkey.com/grass’.