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Published In: Species Plantarum 2: 579. 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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12. Lamium L. (dead nettle)

Plants annual (perennial herbs elsewhere), with taproots. Stems erect or ascending, sometimes from a spreading base, sharply 4-angled, unbranched or branched, glabrous or hairy. Lowermost leaves moderately to long-petiolate, grading into the sessile upper leaves, the petiole unwinged or narrowly winged (in short-petiolate leaves), with a relatively weak, unpleasant fragrance when crushed. Leaf blades ovate to nearly circular or kidney-shaped, the margins toothed or scalloped and sometimes also lobed, the surfaces hairy, the undersurface usually also with inconspicuous, sessile glands. Inflorescences axillary, small clusters of mostly 4–12 flowers per node, the flowers sessile or nearly so, a pair of bractlets absent or inconspicuous, short, and slender. Cleistogamous flowers often produced, these with calyces similar to those of open flowers, but sometimes slightly shorter, and corollas that are only about as long as the calyx lobes and never fully open. Calyces actinomorphic or nearly so (the uppermost lobe often slightly longer than the lower lobes), lacking a lateral projection, symmetric at the base, cylindric to narrowly bell-shaped, the tube 5-nerved, glabrous or sparsely and finely hairy in the mouth, the lobes shorter than to longer than the tube at flowering, triangular to narrowly triangular, tapered to slender, sharply pointed tips, but remaining soft (not spinescent), not or only slightly becoming enlarged but often becoming papery at fruiting. Corollas zygomorphic, pale pink to lavender or pinkish purple, rarely entirely white, the lower lip sometimes lighter or white with purple spots or mottling, the outer surface sparsely to densely hairy, the tube funnelform, relatively shallowly 2-lipped, the upper lip entire or shallowly 2-lobed, concave (appearing hooded), the lower lip spreading, with a conspicuous central lobe that is narrowed at the base and entire to notched at the tip, the lateral lobes short and toothlike, sometimes reduced to small convexities along the lip margin. Stamens 4, not exserted (ascending under the hooded upper corolla lip), the upper 2 stamens with slightly shorter filaments than the lower pair, the anthers small, the connective short, the pollen sacs 2, angled to spreading, purple, reddish purple, or white, densely hairy. Ovary deeply lobed, the style appearing nearly basal from a deep apical notch. Style not exserted, equally 2-branched at the tip. Fruits dry schizocarps, separating into 2–4 nutlets, these 1.5–2.5 mm long, narrowly obovoid to obovoid, more or less truncate at the tip, often with thickened angles, with 2 flat sides and a rounded dorsal face, the surface light brown to grayish brown or olive brown, often with lighter mottling, finely pebbled, glabrous. About 40 species, Europe, Asia; introduced widely in the New World.

The genus Lamium was monographed by Mennema (1989), based primarily on the morphological study of herbarium specimens. Mennema accepted only 16 total species instead of the approximately 40 species accepted my most earlier botanists, treating most of the complexes as single species, each divided into a series of subspecies or varieties. Because his taxonomic conclusions did not take into account the considerable body of biosystematic data on the genus, including the meticulous cytological analyses of artificially produced hybrids performed by Bernström (1955), Mennema’s classification has not been fully embraced by most subsequent botanists.

A few of the rhizomatous perennial species are cultivated as ornamentals and groundcovers, notably L. album L. (white dead nettle), L. galeobdolon (L.) Crantz (Lamiastrum galeobdolon (L.) Ehrend. & Polatschek; yellow archangel) and L. maculatum L. (spotted dead nettle). The two species found in Missouri are disturbance-adapted annuals that often produce conspicuous displays of color in the spring, particularly in crop fields that have not yet been plowed.

 
 
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