The grass genera of the world
Type species: Hopia obtusa (Kunth) Zuloaga & Morrone.
Habit, vegetative morphology. Perennial; rhizomatous. Culms 15–80 cm high; herbaceous. Culm nodes hairy, or glabrous. Culm internodes hollow. Leaf blades linear-lanceolate; narrow; 3.5–20 cm long, 2–4 mm wide; flat (or slightly involute marginally); not pseudopetiolate; persistent. Ligule an unfringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (with ascending first-order branches appressed to the main axis); non-digitate. Rachides triquetrous, neither flattened nor hollowed, not winged. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelets paired; not secund (the rachides not unilateral); shortly subsessile (with the lower spikelet often aborted).
Female-fertile spikelets. Spikelets perfect 3–3.8 mm long; elliptic, or obovate; abaxial; biconvex; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; shorter than the spikelets to about equalling the spikelets (somewhat shorter); long relative to the adjacent lemmas (the upper one subequalling the lower lemma); hairless; not pointed (the upper), or pointed (the lower); awnless; non-carinate. Lower glume only somewhat shorter than the lowest lemma; much longer than half length of lowest lemma; 3–7 nerved. Upper glume 7–11 nerved. Spikelets (the perfect ones) with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male (with three stamens and two lodicules). The proximal lemmas obtuse or acute; awnless; 7–9 nerved; exceeded by the female-fertile lemmas to more or less equalling the female-fertile lemmas.
Female-fertile florets 1. Lemmas obovoid; decidedly firmer than the glumes; becoming indurated; entire; awnless; apically hairy (with simple papillae, macrohairs and microhairs); non-carinate; having the margins inrolled against the palea. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; indurated. Lodicules present; 2. Stamens 3. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Stomata common. Subsidiaries triangular. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type.
Transverse section of leaf blade, physiology. C4. The anatomical organization conventional. Biochemical type NADPME; XyMS. Leaf blade adaxially flat. Midrib not readily distinguishable. Bulliforms present in discrete, regular adaxial groups; in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 20 and 40.
Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 1 species (H. obtusa).
Distribution, phytogeography, ecology. Southwestern United States, northern and central Mexico.
Species of open habitats.
References, etc. Morphological/taxonomic: Zuloaga, F.O. Giussani, L. and Morrone, O. (2007). Hopia, a new monotypic genus segregated from Panicum (Poaceae). Taxon 56(1):145–156. Leaf anatomical: Zuloaga et al. (2007).
Special comments. Fruit data wanting. Illustrations. • H. obtusa: as Panicum, 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’.