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The grass genera of the world

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

Streptogyna P. Beauv.

Including Streptia Doell

Habit, vegetative morphology. Perennial; stoloniferous to caespitose. The flowering culms leafy. Culms 60–100 cm high; herbaceous; to 0.5 cm in diameter; unbranched above. Rhizomes pachymorph. Plants unarmed. Leaves mostly basal (S. americana), or not basally aggregated (S. crinita); auriculate (at the top of the sheath - inconspicuous or absent in S. americana); with auricular setae (better developed in S. crinita). Leaf blades linear to lanceolate; broad; 13–36 mm wide (15–25 cm long); pseudopetiolate, or not pseudopetiolate; cross veined (few laterals, above the base); disarticulating from the sheaths. Ligule a fringed membrane; truncate. Contra-ligule present (in the form of a hard rim).

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

Inflorescence. Inflorescence a single raceme (inilateral, spiciform); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; persistent. Spikelets secund; pedicellate.

Female-fertile spikelets. Spikelets 25–35 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets (the rachilla joint at the base of each floret forming a hook, aiding in dispersal); with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present, or absent.

Glumes two; very unequal (G2 much longer); shorter than the adjacent lemmas; hairless; awnless; papery. Lower glume 1–3(–5) nerved. Upper glume (5–)7–17 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (with glabrous lemmas). The distal incomplete florets merely underdeveloped.

Female-fertile florets 2–4. Lemmas convolute; similar in texture to the glumes to decidedly firmer than the glumes (rigidly leathery); not becoming indurated; incised; 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; from a sinus; non-geniculate; straight; hairless (antrorsely scabrous); much shorter than the body of the lemma to about as long as the body of the lemma. Lemmas hairy (silky villous below the middle); non-carinate; 7–13 nerved. Palea present (narrowly linear); relatively long; apically notched; awnless, without apical setae; not indurated; 2-nerved (these median, contiguous). Lodicules present; 3; free; membranous; ciliate (only inconspicuously so in S. americana); not toothed; heavily vascularized. Stamens 2. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous, or apically hairy. Styles fused (only at the base in S. americana). Stigmas 2 (S. crinita), or 3 (S. americana - in both species, they elongate after anthesis to entangle with one another and with the lemma awns).

Fruit, embryo and seedling. Fruit free from both lemma and palea; large; linear; compressed laterally; when present, with hairs confined to a terminal tuft. Hilum long-linear. Embryo small; not waisted. Endosperm hard; containing only simple starch grains, or containing compound starch grains (some, in S. crinita). Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a short mesocotyl; with a loose coleoptile (with a short mucro). First seedling leaf with a well-developed lamina. The lamina narrow; erect.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; differing markedly in wall thickness costally and intercostally (the costals rather thicker walled). Mid-intercostal long-cells rectangular (mostly); having markedly sinuous walls. Microhairs absent. Stomata common; 18–24 microns long. Subsidiaries dome-shaped (in S. americana), or dome-shaped and triangular (in S. crinita). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (mostly); silicified. Intercostal silica bodies narrowly saddle shaped. Costal short-cells conspicuously in long rows (S. crinita), or predominantly paired (S. americana). Costal silica bodies saddle shaped (predominating), or tall-and-narrow to crescentic; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells (S. crinita), or without arm cells (no trace of these in S. americana); with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous; having complex vascularization (the large keel with an abaxial arc, plus one small adaxial bundle); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (these large); in simple fans. All the vascular bundles accompanied by sclerenchyma (or a few without, in S. crinita). Combined sclerenchyma girders present (with most bundles); forming ‘figures’ (a few with I’s and T’s). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 12. 2n = 24.

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Streptogyneae. Soreng et al. (2015): Oryzoideae; Streptogyneae. 2 species.

Distribution, phytogeography, ecology. Africa, India, Central and South America.

Shade species; glycophytic. In dry forests.

References, etc. Morphological/taxonomic: Soderstrom and Judziewicz 1987. Leaf anatomical: Metcalfe 1960; studied by us - S. americana C.E. Hubb.

Illustrations. • S. crinita: Jacques-Félix, 1962. • S. crinita, leaf blade anatomy: Jacques-Félix, 1962. • S. crinita: P. Beauv. (1812). • S. crinita: Rose Innes, Ghana Grasses (1977)

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.’.