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The grass genera of the world

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

Brachychloa Phillips

Habit, vegetative morphology. Decumbent annual, or perennial; stoloniferous. Culms 15–50 cm high; herbaceous; branched above (sometimes), or unbranched above (usually). Culm nodes glabrous. Culm internodes hollow. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; narrow; 4–6 mm wide; flat; without abaxial multicellular glands; without cross venation; persistent. Ligule a fringed membrane; about 1 mm long.

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

Inflorescence. Inflorescence of spicate main branches; with the branches appressed and often crowded into a loose head in B. schiemanniana, spreading in B. fragilis; non-digitate. Primary inflorescence branches 6–16. Rachides flattened. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. The racemes spikelet bearing to the base. Spikelet-bearing axes disarticulating (B. fragilis), or persistent; when disarticulating, falling entire. Spikelets solitary; secund; biseriate; shortly pedicellate; imbricate.

Female-fertile spikelets. Spikelets 3.5–7 mm long; adaxial; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Callus absent.

Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; lateral to the rachis (by twisting of the pedicels); hairless; glabrous (to minutely scaberulous); pointed; awnless; somewhat carinate; similar (subcoriaceous). Lower glume 1–3 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets awnless.

Female-fertile florets 3–7. Lemmas not saccate; similar in texture to the glumes (membranous); not becoming indurated; incised; blunt; 2 lobed; not deeply cleft (bidentate); very shortly mucronate (from between the lobes); hairy (on the margins, in B. fragilis), or hairless (in B. schiemanniana); carinate; without a germination flap; 3 nerved, or 5–7 nerved (in B. schiemanniana); with the nerves non-confluent. Palea present; relatively long (gibbous); entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; fleshy (?); glabrous; not or scarcely vascularized. Stamens 3. Anthers 0.4 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2; red pigmented (dark purple).

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (0.8 mm long); compressed laterally, or trigonous. Hilum short. Pericarp free.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell (at the same end of each cell, thick walled and pitted). Long-cells differing markedly in wall thickness costally and intercostally (intercostals thicker walled). Intercostal zones with typical long-cells (on focusing through the papillae). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type (but well disguised in this papillate epidermis). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 15 microns long. Microhair total length/width at septum 2. Microhair apical cell/total length ratio 0.3. Stomata common. Subsidiaries non-papillate; dome-shaped (mainly), or triangular. Guard-cells overlapping to flush with the interstomatals (on the side not obscured by a papilla). Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped (very regular).

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheath outlines uneven and even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions present (with some bundles only). Maximum number of extension cells 1. PCR cell chloroplasts centripetal. Leaf blade ‘nodular’ in section to adaxially flat. Midrib conspicuous; having a conventional arc of bundles (a large median, with a smaller lateral at either side); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; seemingly exclusively in simple fans (but these deeply penetrating). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the laterals with I’s). Sclerenchyma all associated with vascular bundles (though the abaxial girders of the keel bundles form three heavy blocks). The lamina margins with fibres.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 2 species (B. fragilis, B. schiemanniana).

Distribution, phytogeography, ecology. Southern Mozambique, Natal.

Mesophytic to xerophytic; shade species and species of open habitats; glycophytic. In coastal forests on sandy soil.

References, etc. Leaf anatomical: studied by us - B. schiemanniana Phillips; photos provided by R.P. Ellis.

Special comments. Generic circumscriptions around Brachychloa, Drake-Brockmania and Heterocarpha seem problematical, especially in the absence of anatomical data for H. haareri and B. fragilis. Illustrations. • B. schiemanniana: Gibbs Russell et al., 1990. • Abaxial epidermis of leaf blade (B. schiemanniana)

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.’.