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Published In: Species Plantarum 2: 584. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/25/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced


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13. Leonurus L.

Plants biennial or perennial herbs (sometimes functionally annual), with taproots or short rhizomes. Stems erect or ascending, sharply 4-angled, unbranched or more commonly branched, mostly with short, soft or stiff, curved or downward-angled hairs (occasionally glabrous). Leaves opposite, mostly short- to long-petiolate (the uppermost leaves sometimes sessile or nearly so), the petioles usually unwinged. Leaf blades variously shaped, unlobed or more commonly 3-lobed or palmately 5–9-lobed, the margins otherwise entire or sharply few-toothed, the surfaces glabrous or variously hairy, the undersurface also with usually conspicuous sessile glands. Inflorescences axillary, dense clusters of numerous flowers per node, these sessile or nearly so. Bractlets shorter than to about as long as the calyces, linear, often spinescent at the tips. Calyces slightly zygomorphic, lacking a lateral projection, symmetric at the base, more or less cylindric below the lobes, the tube 5- or 10-nerved or -ribbed (usually also strongly nerved on the inner surface), glabrous in the mouth (but note that the nutlets are densely bristly-hairy at the tip), the lobes shorter than to about as long as the tube, the upper 2 lobes more or less ascending, the lower 3 lobes noticeably spreading (except sometimes in L. japonicus), narrowly triangular to triangular, tapered to spinescent tips, glabrous or finely short-hairy on the outer surface, becoming slightly enlarged and papery or leathery at fruiting. Corollas 4–14 mm long, zygomorphic, variously white, pale pink, or lavender, the lower lip with darker purple spots, but lacking small nipplelike projections, the outer surface moderately to densely hairy, the tube narrowly funnelform, 2-lipped, the lips about as long as to slightly longer than the tube, the upper lip entire at the broadly rounded tip, somewhat hooded, the lower lip 3-lobed, spreading, with the central lobe longer than the 2, lateral lobes. Stamens 4, not exserted (the upper pair curved under the upper lip, the lower pair with the anthers positioned just above the corolla throat), the filaments of 2 lengths, the anthers small, the connective somewhat expanded, the pollen sacs 2, parallel or spreading (in L. marrubiastrum), dark purple. Ovary relatively shallowly lobed, the style appearing more or less lateral from a shallow apical notch. Style not exserted, with 2, short, equal or unequal branches at the tip. Fruits dry schizocarps, separating into usually 4 nutlets, these 1.5–2.5 mm long, more or less wedge-shaped to obovate in outline, obliquely truncate to broadly rounded at the tip, unequally triangular in cross-section, the surface yellowish brown to reddish brown or brown, sometimes with irregular, lighter, tan to yellow mottling, usually finely and minutely hairy except for the densely hairy tip, otherwise relatively smooth. Twenty-three to 27 species, species, Europe, Asia, Africa; introduced in the New World.

A case can be made for splitting Leonurus into three genera, segregating two Eurasian species that have not been introduced into the United States into Panzerina Soják and the widespread L. marrubiastrum into Chaiturus Willd. (Krestovskaja, 1992; H.-w. Li and Hedge, 1994). The morphological and cytological features that characterize these small segregates need to be evaluated in a phylogenetic context, and many recent authors have continued to treat the genus in the broad sense, a practice followed for the time being in the present treatment.

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