The grass genera of the world
Including Pogochloa S. Moore, Schenkochloa
Habit, vegetative morphology. Perennial. Culms 30–350 cm high; woody and persistent (sometimes, somewhat), or herbaceous; scandent (in one species), or not scandent; branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear-lanceolate; broad, or narrow; flat, or rolled (involute); without abaxial multicellular glands; not pseudopetiolate; without cross venation. Ligule a fringed membrane, or a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches; open; non-digitate (the branches racemosely arranged); espatheate; not comprising partial inflorescences and foliar organs. The racemes without spikelets towards the base. Spikelet-bearing axes with very slender rachides; persistent. Spikelets solitary; secund; biseriate; subsessile to pedicellate.
Female-fertile spikelets. Spikelets 6–15 mm long; adaxial; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets. Hairy callus present. Callus short; blunt.
Glumes present; two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis; pointed (to attenuate); awnless; carinate; similar (lanceolate). Lower glume shorter than the lowest lemma; 1–5 nerved. Upper glume (1–)3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped; awned (awned or reduced to the awn, by contrast with Leptochloa). Spikelets without proximal incomplete florets.
Female-fertile florets 2–5. Lemmas similar in texture to the glumes (thin); not becoming indurated; entire, or incised; pointed, or blunt; when incised, 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; from a sinus, or apical; non-geniculate; hairless (scabrid); much shorter than the body of the lemma (rarely), or about as long as the body of the lemma to much longer than the body of the lemma; persistent. Lemmas hairy (densely ciliate below adjoining the midnerve, and often ciliate or pilose on the margins); carinate; without a germination flap; 3 nerved, or 5(–7) nerved; with the nerves confluent towards the tip. Palea present; relatively long, or conspicuous but relatively short; apically notched (two-toothed); awnless, without apical setae, or with apical setae to awned (via the teeth); textured like the lemma; not indurated; 2-nerved; 2-keeled. Palea keels somewhat winged. Lodicules present; 2 (tiny); free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers about 0.5 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (3–4 mm long); brown or black; ellipsoid; strongly longitudinally grooved (ventrally); compressed laterally (slightly); smooth. Hilum long-linear. Pericarp fused. Embryo small (i.e. generally less than a third of the fruit length); not waisted. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (in G. latifolia, Diaz 1993), or absent (mostly); in G. latifolia, intercostal. Intercostal papillae not over-arching the stomata. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (these pitted). Microhairs present; elongated; clearly two-celled; panicoid-type to chloridoid-type (but fairly narrow, with longish basal cells). Microhair apical cell wall thinner than that of the basal cell but not tending to collapse. Microhairs (28.5–)31–36(–37.5) microns long. Microhair basal cells 21 microns long. Microhairs (7.5–)8.4–11.4(–11.7) microns wide at the septum. Microhair total length/width at septum 2.9–5. Microhair apical cells 10–13.5 microns long. Microhair apical cell/total length ratio 0.32–0.43. Stomata common; 18–22.5 microns long. Subsidiaries dome-shaped, or triangular (but their apices truncated). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies present and perfectly developed; tall-and-narrow and oryzoid-type. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; mostly dumb-bell shaped (short to elongated).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines uneven (the abaxial 2 or 3 PCR cells very small, the lower laterals much wider than the upper ones). PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Leaf blade adaxially flat (or the ribs broad and flat topped, scarcely prominent). Midrib conspicuous; having a conventional arc of bundles (one large median bundle, with two laterals on either side); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (only one example of the latter seen, but the simple fans all with deeply penetrating median cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all but those in the midrib); forming figures (all the lateral bundles with conspicuous Is). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 40 (where available, but with n counts of 20, 32, 38 and 40).
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Gouiniinae. 9 species (according to Diaz, 1993).
Distribution, phytogeography, ecology. Mexico to Argentina, West Indies.
Shade species and species of open habitats. Thickets and open places on hill slopes.
Rusts and smuts. Rusts Puccinia.
References, etc. Morphological/taxonomic: Swallen 1935. Leaf anatomical: this project.
Illustrations. • G. paraguayensis: 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: 13th November 2017. delta-intkey.com/grass’.