Open Herbarium - Dichanthelium acuminatum

Dichanthelium acuminatum (Sw.) Gould & C.A. Clark
Family: Poaceae Hairy Panicgrass Linda Ann Vorobik and Hana Pazdírková, Illustrators	Flora of North America Resources Robert W. Freckmann and Michel G. Lelong Plants more or less densely cespitose. Basal rosettes usually well-differentiated; blades ovate to lanceolate. Culms15-100 cm (rarely taller), usually thicker than 1 mm, weak and wiry or relatively stout and rigid, erect, ascending or decumbent; nodes occasionally swollen, glabrous or densely pubescent, often with a glabrous or viscid ring below; internodes purplish or olive green or grayish-green, to yellowish-green, variously pubescent, with hairs of 2 lengths or glabrous; fall phase erect, spreading, or decumbent, usually branching extensively at all but the uppermost nodes, ultimately forming dense fascicles of branchlets with reduced, flat or involute blades and reduced secondary panicles with few spikelets. Cauline leaves 4-7; sheaths usually shorter than the internodes, glabrous or densely and variously pubescent with hairs shorter than 3 mm, margins ciliate or glabrous; ligules and pseudoligules 1-5 mm, of hairs; blades 2-12 cm long (rarely longer), 2-12 mm wide (rarely wider), firm or lax, spreading to reflexed or stiffly ascending, yellowish-green or grayish-green to olivaceous, densely to sparsely and variously pubescent, margins similar or occasionally whitish-scabridulous, margins often with papillose-based cilia, at least basally, bases rounded or subcordate. Primary panicles 3-12 cm, 1/4-3/4 as wide as long, usually open, well-exserted, rather dense; rachises glabrous, puberulent, or more or less densely pilose, at least basally. Spikelets 1.1-2.1 mm, obovoid to ellipsoid, yellowish-green to olivaceous or purplish, variously pubescent, obtuse or subacute. Lower glumesusually 1/4-1/2 as long as the spikelets, obtuse to acute; upper glumes and lower lemmas subequal, equaling the upper florets at maturity, or occasionally the upper glumes slightly shorter, not strongly veined; lower floretssterile; upper florets 1.1-1.7 mm long, 0.6-1 mm wide, ellipsoid, obtuse to acute or minutely umbonate or apiculate. 2n = 18. Dichanthelium acuminatum is common and ubiquitous in dry to wet, open, sandy or clayey woods, clearings, bogs, and swamps, or in saline soil near hot springs, growing in much of the Flora region and extending into northern South America. It is probably the most polymorphic and troublesome species in the genus. The treatment presented here attempts to delimit the major variants present, but does not fully reflect the intricate reticulate pattern of morphological variation that exists. There is considerable overlap among the nine subspecies recognized and, in addition, there appears to be widespread introgression from other Dichanthelium species, such as D. dichotomum, D. sphaerocarpon, D. ovale, and D. aciculare into the D. acuminatum complex, contributing to the taxonomic difficulties.
Open Interactive Map Linda Ann Vorobik and Hana Pazdírková, Illustrators Click to Display 2 Total Images