DELTA home

The grass genera of the world

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

Streptochaeta Schrad.

Including Lepideilema Trin.

Habit, vegetative morphology. Perennial; rhizomatous (the internodes crowded). The flowering culms leafy. Culms 35–105 cm high; woody and persistent; to 0.3 cm in diameter; branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes hollow. Pluricaespitose. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; spirally disposed; auriculate (from the sheath); with auricular setae. The juncture of blade and sheath a smooth, dark band of tissue covered by cilia abaxially. Leaf blades lanceolate to ovate; broad; (5–)10–95 mm wide; pseudopetiolate; palmately veined to pinnately veined (in that the veins converge into the midrib from a distance of several cm above the base of the lamina); cross veined; disarticulating from the sheaths. Ligule a fringe of hairs. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. Not viviparous.

Inflorescence. Inflorescence determinate; with pseudospikelets, or without pseudospikelets (depending on interpretation: buds sometimes present in the ‘bract’ axils, but these seemingly not proliferating); a single raceme (or a raceme of spikes, if the ‘spikelet’ be so interpreted). Inflorescence with axes ending in spikelets, or axes not ending in spikelets (sometimes ending in a tuft of hairs). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spikes; persistent (tough). Spikelets solitary; not secund; not two-ranked (the raceme many-sided); pedicellate. Pedicel apices cupuliform.

Female-fertile spikelets. Spikelets unconventional (with 5 spirally arranged, dentate ‘bracts’ (?glumes, sometimes with axillary buds), a sixth produced into a very long, coiled awn, 7 and 8 side by side opposing 6, and 9–11 whorled to form a central cone, lemma, palea and lodicules absent); 10–20 mm long; not noticeably compressed; falling with the glumes (all the pseudospikelets of the inflorescence often shed as a unit, entangled via the long awns of their G6’s which are deflected by the central cones into the cleft between bracts 7 and eight). Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes present; several (in the form of 11 or twelve ‘bracts’, as described elsewhere, the lowermost to 4 mm long, the uppermost to 15 mm); very unequal; hairless; awned (the G6 with a long, coiled, terminal awn), or awnless (the rest); non-carinate. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas absent, or at least unrecognisable. Palea present; convolute around the flower, or not convolute. Lodicules absent. Stamens 6; monadelphous. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused. Stigmas 3.

Fruit, embryo and seedling. Fruit free from both lemma and palea; linear; not grooved; not noticeably compressed (terete). Hilum long-linear. Pericarp loosely adherent to fused. Embryo small. Endosperm hard; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with a negligible mesocotyl internode; with more than one scutellum bundle. Embryonic leaf margins overlapping.

Seedling with a short mesocotyl; with a loose coleoptile. First seedling leaf without a lamina.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular and fusiform (but the latter forms asymmetric, reflecting oblique end-walls); having markedly sinuous walls. Microhairs present; panicoid-type; (84–)90–96(–99) microns long; (6–)7.5–9 microns wide at the septum. Microhair total length/width at septum 9.3–13.2. Microhair apical cells (43.5–)58.5–66(–69) microns long. Microhair apical cell/total length ratio 0.52–0.72. Stomata common; 24–33 microns long. Subsidiaries high dome-shaped, or parallel-sided. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies exclusively saddle shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without arm cells (or at least without conspicuous arm cells, in the material seen); with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous (via a T-shaped adaxial rib and a small, rounded, abaxial keel); having complex vascularization (there being a small bundle adaxial to the main one); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (these large and wide); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 11. 2n = 22. 2 ploid.

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Streptochaeteae. Soreng et al. (2015): Anomochlooideae; Streptochaeteae. 3 species.

Distribution, phytogeography, ecology. Mexicoto Argentina.

Shade species.

References, etc. Morphological/taxonomic: Judziewicz and Soderstrom 1989. Leaf anatomical: Metcalfe 1960; dtudied by us - S. spicata Schrad. ex Nees.

Illustrations. • S. spicata, general aspect: Trinius (1836), Species Graminum 3. • S. spicata, technical details: Trinius (1836), Species Graminum 3. • S. spicata: Nicora & Rúgolo de Agrasar (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.’.