14. Lycopus L. (bugleweed)
(Henderson, 1962)
Plants perennial
herbs, with rhizomes, often with stolons, sometimes producing small tubers.
Stems erect or ascending, occasionally reclining on surrounding vegetation,
bluntly or sharply 4-angled (except sometimes in swollen, spongy,
submerged-aquatic stems), unbranched or branched, variously glabrous to densely
hairy. Leaves opposite, sessile or short-petiolate (the petioles occasionally
relatively long in L. rubellus), the petioles then winged most of their
length, with a pungent, disagreeable odor when bruised or crushed. Leaf blades
variously shaped, unlobed to pinnately deeply several-lobed, the margins
otherwise entire or sharply toothed, the surfaces glabrous or hairy, 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 to lanceolate, tapered to sharply
pointed but not spinescent tips. Calyces not or only slightly zygomorphic,
lacking a lateral projection, symmetric at the base, more or less cylindric to
broadly bell-shaped, the tube with 4 or 5 fine main nerves (1 per lobe), in
some species with a pair of fainter lateral nerves, glabrous in the mouth, the
lobes much shorter than to about as long as the tube, ascending or spreading,
broadly to narrowly triangular, rounded to more commonly angled or tapered to
bluntly or sharply pointed but not spinescent tips, glabrous or finely short-hairy
on the outer surface and along the lobe margins, sometimes also glandular, not
becoming enlarged or papery at fruiting. Corollas 2.5–5.0 mm long,
actinomorphic or nearly so (not 2-lipped), white, sometimes with faint to
prominent, darker purple spots on some of the lobes, the outer surface glabrous
or more commonly moderately to densely glandular, the tube funnelform, 4 or 5
lobes more or less similar (if 4-lobed then the upper lobe slightly larger than
the others), shorter than the tube, the throat closed with a dense beard of
multicellular hairs. Stamens 2, not or only slightly exserted, the anthers
minute, the connective short, the pollen sacs 2, spreading, white, yellow, or
dark purple. Ovary deeply lobed, the style appearing more or less basal from a
deep apical notch. Style not or only slightly exserted, with 2, short, equal
branches at the tip. Fruits dry schizocarps, separating into usually 4 nutlets,
these 1.0–2.3 mm long, more or less tetrahedral, broadly rounded to truncate at
the tip, unequally triangular in cross-section, with a corky winglike structure
oriented vertically along the lateral margins and across the apex, the surface
yellowish brown to reddish brown or brown (the corky band often somewhat
lighter), relatively smooth (sometimes minutely roughened toward the tip),
usually glandular. Fourteen to 16 species, North America, Europe, Asia;
disjunct in Australia, Tasmania.
Steyermark
(1963) noted that the tubers produced by most species of Lycopus are
eaten by muskrats.
Species of Lycopus
superficially resemble Spermacoce glabra Michx. (Buttonweed) in the
Rubiaceae, which also has dense axillary clusters of small white flowers. Spermacoce
glabra differs in its ovary position (inferior vs. superior); fruit type
(unlobed and achenelike vs. nutlets), deeply lobed, unnerved calyces (vs.
shallowly lobed or to about the midpoint and strongly nerved), and 4 (vs. 2)
stamens, among other characters.