Disakisperma Steud.

Le résumé fourni par la source

Disakisperma Steud., Syn. Pl. Glumac. 1: 287 (1854). Type. Disakisperma mexicana Steud. = Disakisperma dubium (Kunth) P. M. Peterson & N. Snow ≡ Chloris dubia Kunth. Diagnosis. Disakisperma differs morphologically from Cypholepis most notably in having cleistogamous inflorescences in the lower leaf sheaths (v. no cleistogamous spikelets in the lower sheaths) and lemmas with acute- or round-tipped hairs (v. lemmas with clavate or clavicorniclate-tipped hairs). Description. (amended from Peterson et al. 2012 and Snow et al. 2013) Caespitose perennials. Culms (10 –) 30–110 cm tall, 1.0– 4.5 mm wide at base, round or flattened, mostly erect or infrequently sprawling, from fibrous root crowns, with hidden (fully inserted) cleistogamous inflorescences in lower leaf sheaths; nodes glabrous. Leaf sheaths longer (typically proximally) or shorter (distally) than internodes, typically sparsely hairy below and sometimes densely so near collar, hair bases sometimes tuberculate; ligules 1.0– 1.5 mm long, membranous, truncate and apically short-ciliate; blades (2 –) 8–35 mm long, scabrous near base or sparsely hairy above, glabrous to minutely scabrous below, flat or drying involute. Cleistogamous panicles completely inserted in lower sheaths. Terminal panicles 10–45 cm long, (2 –) 5–25 cm wide, mostly exserted at maturity; branches composed of (2 –) 5–15 unilateral racemes, racemosely or less frequently sub-digitately arising from the rachis, these ascending to reflexed and often slightly flexuous. Spikelets (4 –) 12 mm long, 4–13 - flowered, sessile to subsessile, dorsally rounded at maturity, overlapping to distant, disarticulation above the glumes; callus glabrous; glumes 2; lower glumes (1.6 –) 2.3–4.8 mm long, 1 - veined, membranous; upper glumes 3.3–5.0 mm long, 1 - veined, membranous; lemmas 4–5 mm long, ovate to obovate or widely obovate, usually 3 - veined or sometimes 4–5 - veined near base, membranous, sometimes cartilaginous near base, sericeous along lower portions of lateral veins and sometimes on midvein and between veins, hairs acute or rounded apically, apex broadly acute to obtuse or truncate, awnless or mucronate, often bifid; paleas subequal to lemma, ciliate on margins and sometimes sericeous between veins. Flowers perfect; lodicule number not confirmed; stamens 3; anthers 1.0– 1.6 mm long, yellow. Caryopses 1.9–2.3 mm long, dorsally flattened, broadly to shallowly concave on the hilar surface; pericarp weakly adnate to endosperm. Chromosome numbers. n = 20 (Gould 1960; Valls 1978); 2 n = 40 (Covas 1949; Gould 1960, 1966, 1968), 2 n = 60 (Brown 1950), 2 n = 80 (Gould 1960, 1965; Valls 1978). Species included. Disakisperma dubium (Kunth) P. M. Peterson & N. Snow [for complete nomenclatural summary see Snow et al. 2013]. Distribution. Native: In the USA from Arizona to Oklahoma and Texas, and disjunct in southern Florida, in much of Mexico, sporadically in the Caribbean and in Mesoamerica to Bolivia and Chile east to Paraguay, Uruguay, and Argentina; in a variety of vegetation and soil types (including limestone), but most frequently on well drained slopes, mostly 100–2500 m, to 3150 m in the Andes of South America. Non-native: USA in California, Hawaii (Snow and Davidse 2011), Kansas, and Missouri. Its occurrences in the high Andes of Colombia, Ecuador, Bolivia, and Peru may be as introductions (Snow et al. 2013).

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.