The grass genera of the world
~ Eragrostis (E. reptans)
Habit, vegetative morphology. Annual; stoloniferous, or decumbent. Culms 5–15 cm high; herbaceous. Leaves not basally aggregated; non-auriculate. Leaf blades linear (acuminate); narrow; 1.5–3 mm wide (1–3 cm long); flat; without abaxial multicellular glands; without cross venation. Ligule a fringe of hairs; 0.5–1 mm long.
Reproductive organization. Plants dioecious; without hermaphrodite florets. The spikelets all alike in sexuality (on the one plant); female-only, or male-only. Plants outbreeding.
Inflorescence. Inflorescence of spicate main branches (in the male), or paniculate (in the female); very contracted (in the female); capitate (in the female, subcapitate in the male); digitate (in the male), or non-digitate (in the densely contracted female panicles); espatheate; not comprising partial inflorescences and foliar organs. Spikelets secund (male), or not secund (female); biseriate (male), or not two-ranked (female); subsessile to pedicellate.
Female-sterile spikelets. Male spikelets about 8 mm long, many-floreted, glumes unequal, lemmas 3 nerved; palea almost as long as lemma, 2-keeled; 2 fleshy lodicules, 3 stamens 1.5–2.5 mm long. Rachilla of male spikelets prolonged beyond the uppermost male floret. The male spikelets with glumes; without proximal incomplete florets; about 8–15 floreted. Male florets about 8–12; 3 staminate.
Female-fertile spikelets. Spikelets about 5–6 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets (the rachilla and paleas persistent). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus absent.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; pointed; awnless; similar. Lower glume 1 nerved. Upper glume 1–2 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awnless.
Female-fertile florets about 8–12. Lemmas similar in texture to the glumes; not becoming indurated; entire; pointed (acuminate); awnless; often hairy (sparsely villous); carinate; 3 nerved. Palea present; conspicuous but relatively short (about half as long as the lemma); awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Palea keels wingless; hairy. Lodicules present; 2; free; fleshy; glabrous. Stamens 0. Ovary apically glabrous. Styles basally fused (forming a persistent beak on the fruit). Stigmas 2 (conspicuously emergent at anthesis).
Fruit, embryo and seedling. Fruit small (0.8–0.9 mm long); ellipsoid; compressed laterally. Hilum short. Pericarp fused. Embryo large (0.3–0.4 mm long); waisted. Endosperm hard. Embryo with an epiblast.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; Enneapogon-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 90–250 microns long. Microhair basal cells 130–230 microns long. Microhair total length/width at septum 10–15. Microhair apical cells 15–25 microns long. Microhair apical cell/total length ratio about 0.1–0.2. Stomata common. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies present and perfectly developed; tall-and-narrow, or cubical. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Leaf blade with distinct, prominent adaxial ribs to nodular in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; seemingly exclusively in simple fans. All the vascular bundles accompanied by sclerenchyma. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Eragrostidinae. 1–3 species.
Distribution, phytogeography, ecology. Southern U.S.A., Mexico to Surinam.
Mesophytic; species of open habitats; glycophytic. River banks, sandy and open ground.
References, etc. Morphological/taxonomic: Nicora 1962. Leaf anatomical: Nicora 1962.
Special comments. Very distinct from typical Eragrostis, judging from Nicoras thorough description; but the distinction is blurred by (e.g.) E. hypnoides (Lam.) B.S.P. and especially by E. contrerasii Pohl, which is also dioecious with creeping habit. Illustrations. • N. reptans (as Eragrostis): Hitchcock and Chase (1950)
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. delta-intkey.com/grass’.