The grass genera of the world
Including Eremochloe S. Wats.
Habit, vegetative morphology. Usually perennial, or annual (rarely); branching above, with leafy inflorescence tufts on long internodes. Culms 8–20 cm high; herbaceous; branched above. Leaves mostly basal (in tufts); non-auriculate. Leaf blades narrow; acicular (involute, arcuate and rigid, less than 1 mm broad); without abaxial multicellular glands; without cross venation; persistent. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted; paniculate (of peduncled clusters, each invested by spathes); the individual clusters capitate; spatheate (the leaves subtending inflorescences with spathe-like sheaths); a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes very much reduced and paniculate (short, congested, usually surpassed by subtending leaves); persistent. Spikelets associated with bractiform involucres; not secund (?); subsessile.
Female-fertile spikelets. Spikelets 6–8 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present (at the base of the unit as shed). Callus short; blunt.
Glumes two; more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; pointed (acuminate); shortly awned, or awnless (then mucronate); similar (hyaline, shiny). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets both distal and proximal to the female-fertile florets (L1 and L2 sterile or male, deeply lobed and awned, L4 reduced to a 3-awned rudiment). The distal incomplete florets clearly specialised and modified in form; awned (the terminal floret reduced to three awns). Spikelets with proximal incomplete florets. The proximal incomplete florets 2; paleate. Palea of the proximal incomplete florets usually reduced. The proximal incomplete florets male, or sterile. The proximal lemmas shortly awned (and hairy); 3 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas (and similar in form); not becoming indurated.
Female-fertile florets 1 (only L3 fertile). Lemmas not becoming indurated; incised; 2 lobed; deeply cleft; awned. Awns 1, or 3; median, or median and lateral (via the awn-tipped lateral lobes); the median similar in form to the laterals (when laterals present); from a sinus; non-geniculate. The lateral awns when present, shorter than the median. Lemmas hairy (on the margins); non-carinate; without a germination flap; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels hairy. Lodicules absent. Stamens (1–)2, or 3. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit small (about 2 mm long); ellipsoid; compressed laterally. Hilum short. Pericarp fused. Embryo large; without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent (though abundant adaxially). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent (seemingly, from the material seen - though they would be easy to overlook in such material, with the intercostal zones in deep grooves and obscured by prickles or hairs. None seen adaxially either, in B. kingii). Stomata common; (21–)24–28(–30) microns long. Subsidiaries low dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. A few costal prickles forming a continuous series with the abundant macrohairs in B. bigelovii, and abundant prickles in B. kingii. Crown cells absent. Costal short-cells predominantly paired (in places, in both species), or neither distinctly grouped into long rows nor predominantly paired (elsewhere, in both species). Costal silica bodies present throughout the costal zones; rounded, or saddle shaped, or panicoid-type (B. bigelovii with predominantly saddles merging into rounded forms and few panicoid types, B. kingii with mainly panicoid types and few saddles); when panicoid type, cross shaped (irregular), or dumb-bell shaped (short).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Leaf blade nodular in section; with the ribs more or less constant in size (round topped). Midrib fairly conspicuous, or not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (every bundle except the midrib with a massive abaxial strand and a smaller adaxial one, in B. kingii), or present (in B. bigelovii); forming figures (the midrib in B. kingii, all the bundles in B. bigelovii). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Scleropogoninae. 3 species.
Distribution, phytogeography, ecology. U.S.A. and Argentina.
Xerophytic; species of open habitats. Deserts, rocky slopes and xerophyllous scrub.
References, etc. Leaf anatomical: this project.
Illustrations. • B. kingii: Hitchcock and Chase (1950). • B. bigelovii: Hitchcock and Chase (1950). • Blepharidachne sp., TS of leaf blade: this project
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: 13th November 2017. delta-intkey.com/grass’.