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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Holcolemma Stapf & C.E. Hubb.

Type species: Type: H. canaliculatum (Nees) Stapf & C.E.Hubb.

Habit, vegetative morphology. Annual, or perennial; loosely caespitose (with a knotty rootstock and geniculately ascending culms). Culms 30–60 cm high; herbaceous. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; not pseudopetiolate; without cross venation; persistent. Ligule a fringed membrane; very short.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; contracted; spicate. Inflorescence axes not ending in spikelets (at least the larger branchlets terminated by a usually fairly inconspicuous bristle, which subtends the ‘terminal’ spikelet). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets (at least at the branch tips) subtended by solitary ‘bristles’. The ‘bristles’ persisting on the axis. Spikelets not secund.

Female-fertile spikelets. Spikelets 2.5–3.5 mm long; abaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal (G1 a quarter, G2 a half the spikelet length); shorter than the spikelets; shorter than the adjacent lemmas; hairless; pointed, or not pointed; awnless; non-carinate; similar (membranous or chartaceous). Lower glume 3–9 nerved. Upper glume 3–5 nerved, or 11 nerved, or 13 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed; becoming conspicuously hardened and enlarged laterally (after anthesis, when the large leathery keels come to clasp the side of the upper floret). The proximal incomplete florets male, or sterile. The proximal lemmas doubly saccate, with a deep, grooved fold down the back; awnless; 5–13 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas (the L2 sometimes much the shorter); less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (membranous or herbaceous); not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes; rugose; becoming indurated (thinly crustaceous), or not becoming indurated; entire; pointed; awnless, or mucronate; hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 5 nerved. Palea present; relatively long; textured like the lemma; indurated, or not indurated; 2-nerved; 2-keeled. Lodicules present; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones exhibiting many atypical long-cells (typical long-cells only alongside the veins: the rest rounded, irregular or isodiametric). Mid-intercostal long-cells rectangular, or fusiform; long-cells bordering veins sinuous, most intercostal cells not sinuous. Microhairs present; panicoid-type; (52.5–)54–57(–60) microns long; 7.5–9 microns wide at the septum. Microhair total length/width at septum 6.2–7.2. Microhair apical cells 30–34.5 microns long. Microhair apical cell/total length ratio 0.53–0.61. Stomata common (but only alongside veins); 40–46.5 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; mostly dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type. Leaf blade ‘nodular’ in section to adaxially flat. Midrib with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 4 species.

Distribution, phytogeography, ecology. East Africa, southern India, Sri Lanka, Queensland.

Shade species, or species of open habitats. Weedy places.

References, etc. Morphological/taxonomic: Stapf and Hubbard 1929; Clayton 1978a. Leaf anatomical: studied by us - H. canaliculatum (Steud.) Stapf & Hubbard.

Illustrations. • H. inaequale: Ibrahim & Kabuye, Kenya Grasses (1987). • H. canaliculatum, as H. transiens: Ibrahim & Kabuye, Kenya Grasses (1987)

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.’.