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Published In: Species Plantarum 1: 358. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 9/22/2017)
Acceptance : Accepted
 

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1. Dirca L.(leatherwood) (Floden et al., 2009)

Plants shrubs, occasionally somewhat colonial from rhizomes. Stems ascending, branched, thickened and jointed at the nodes. Twigs yellowish brown or occasionally yellowish green, glabrous or hairy, with scattered small lenticels, the developing buds hidden in the hollow petiole bases of existing leaves, eventually exposed, densely hairy. Leaves alternate, simple, short-petiolate to nearly sessile. Stipules absent. Leaf blades simple and unlobed, oblong-ovate to broadly elliptic, ovate, or broadly oblong-ovate, the surfaces variously glabrous or finely hairy (especially the undersurface), the margins entire but often with fine, more or less appressed to spreading hairs. Inflorescences produced before the leaves or as they develop, axillary, sessile or stalked clusters of 2–6 nodding flowers, the bud ellipsoid to oblong-obovoid, with 4 bracts, the outer 2 shed as the flowers develop, the inner 2 persistent and becoming leaflike, sparsely hairy on the upper surface, densely woolly on the undersurface. Flowers perfect, strongly perigynous (the hypanthium appearing as a calyx tube), actinomorphic, not subtended by bractlets. Calyces appearing narrowly funnelform to nearly tubular, consisting of a calyxlike, green to yellowish green basal portion (the hypanthium) and a slightly expanded, petaloid (yellow to lemon yellow), apical portion (the limb) formed from 4 fused sepals, the tip truncate or with 4 shallow, uneven, rounded to broadly triangular lobes, otherwise appearing somewhat irregularly scalloped and/or toothed, not persistent at fruiting. Corollas absent, but sometimes minute petaloid scales are present on the inner surface of the calyx between the attachment points of the stamens. Stamens 8, exserted, the filaments of 2 lengths, attached in a ring to the inner surface of the calyx above the hypanthium portion, the anthers small, attached basally, yellow. Pistil 1 per flower, appearing composed of 1 carpel, the superior ovary sometimes with a minute, irregularly lobed nectar disc at the base. Style 1, slender, exserted and extending slightly beyond the anthers, not persistent at fruiting, the stigma 1, minute, capitate. Ovules 1, the placentation more or less basal. Fruits drupes, shed quickly, the seed enclosed in a thin, hard (stony) inner layer, covered with a thin fleshy layer and a thin, leathery outer layer, this pale yellowish green to nearly white, turning orange to reddish purple with age. Seed 1, broadly ovoid, the bony outer coating with a shallow longitudinal groove along 1 side, smooth, brown to dark brown, sometimes finely and faintly mottled. Four species, North America.

The genus Dirca is currently known to consist of one relatively widespread species and three uncommon species with limited distributions. In addition to the two species treated below, D. occidentalis A. Gray is endemic to coastal northern California and D. mexicana G.L. Nesom & Mayfield is known only from a small area in northeastern Mexico.

The stems of Dirca species are relatively slightly lignified, with very light wood (Nevling, 1962). They are surprisingly flexible and have been used in cordage and baskets. Like most members of the Thymelaeaceae, Dirca is considered to be toxic. The plants contain daphnane ester diterpenoids that can cause strong contact dermatitis (Burrows and Tyrl, 2001), but the tissues have a bitter flavor; thus are not likely to be consumed in quantity by humans or livestock. The fruits can also cause a strong allergic reaction in the mouth and throat, and apparently also have narcotic effects (Burrows and Tyrl, 2001), although reports of dizziness and stupor are largely anecdotal to date.

 
 
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