The grass genera of the world
Including Davyella Hack., Stapfia Davy
Habit, vegetative morphology. Viscid annual; culms ascendng from the decumbent base. Culms 7–30 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. The shoots aromatic. Leaves not basally aggregated; not clearly differentiated into sheath and blade; spirally disposed (seemingly, in material seen); non-auriculate. Leaf blades broad to narrow; 5–12 mm wide (not distinctly separated from the sheaths, 5–10 cm long, the leaves about 12 mm wide in middle); exhibiting multicellular glands abaxially. The abaxial leaf blade glands on the blade margins. Leaf blades not pseudopetiolate; without cross venation; persistent. Ligule absent. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (interpreting the terminal inflorescence bracts as abortivente spikelets); hermaphrodite and sterile.
Inflorescence. Inflorescence a single raceme (dense, spicate, the spikelets spiralled); contracted; soft, dense, 3–7 cm long. Inflorescence axes not ending in spikelets (the upper part of the inflorescence axis with linear-lanceolate, empty bracts instead of spikelets). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate (the pedicels persistent).
Female-fertile spikelets. Spikelets unconventional (not only lacking glumes, but having the lemmas spiralled on the rachilla); 6–7 mm long; compressed dorsiventrally; falling from their pedicels, above the glume vestiges; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes absent. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (the rachilla ending in an incomplete floret). The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 2–5. Lemmas conspicuously non-distichous; flabellate, broad, fringed; not becoming indurated (thinly membranous); entire; blunt; awnless; hairless; non-carinate; without a germination flap; 9–15 nerved. Palea present (narrower than the lemma); relatively long (somewhat shorter than the lemma); apically notched; awnless, without apical setae; not indurated (hyaline); 2-nerved; 2-keeled. Palea keels glabrous. Lodicules present; 2; free; fleshy; ciliate, or glabrous; not or scarcely vascularized. Stamens 3 (the filaments short and thick). Anthers long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit compressed laterally. Hilum short (large). Pericarp with a thick, viscid pericarp, obscuring the embryo. Embryo large (but obscured); with an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking (and no short-cell/ long-cell organisation). Papillae absent. Intercostal zones without typical long-cells. Mid-intercostal long-cells epidermal walls straight. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type (button-mushroom type, cf. Orcuttia). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 6–9 microns long. Microhair total length/width at septum 3.1. Microhair apical cell/total length ratio 0.48. Stomata common; (21–)22.5–24 microns long. Subsidiaries tall dome-shaped (but the guard-cells are not typically poaceous). Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. With crozier macrohairs, plus large capitate multicellular glands, especially at the blade margins. Costal zones without short-cells. Costal short-cells lacking. Costal silica bodies absent.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade nodular in section to adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (and in irregular groups). Many of the smallest vascular bundles unaccompanied by sclerenchyma (in fact, all the bundles lack sclerenchyma accompaniment). Combined sclerenchyma girders absent.
Culm anatomy. Culm internode bundles scattered.
Cytology. Chromosome base number, x = 10. 2n = 40. 4 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; Orcuttieae. Soreng et al. (2015): Chloridoideae; Cynodonteae; Orcuttiinae. 1 species.
Distribution, phytogeography, ecology. Southwestern U.S.A.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Special comments. Fruit data wanting. Illustrations. • N. colusana: 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: 13th November 2017. delta-intkey.com/grass’.