2. Lobelia L. (lobelia)
Plants annual or
perennial herbs (woody elsewhere) usually with milky juice. Leaves sessile to
shortly petiolate, lanceolate to oblanceolate or ovate, the margins finely to
coarsely toothed. Inflorescences terminal spikes, racemes or panicles, the
flowers from the axils of mostly reduced (shorter and narrower than the leaves)
bracts. Flowers more or less epigynous, resupinate (inverted by twisting of the
stalk), not cleistogamous. Calyces all 5-lobed, more or less actinomorphic, the
tube usually ribbed, the lobes usually longer than the tube, sometimes with
short, reflexed appendages (auricles) toward the base alternating with the
lobes. Corollas zygomorphic, strongly 2-lipped with spreading lobes, the
apparent lower lip 3-lobed, the upper lip 2-lobed and split nearly to the base
through which the stamens and style are exserted, the tube sometimes with
slitlike openings (fenestrate), red, or blue to white (rarely purple). Stamens
5, free from the corolla, the filaments free at the very base but mostly fused
into a tube, the anthers also united into a ring around the style, the lower 2
anthers usually shorter than the others and with white tufts of hair. Pistil
with 2 carpels. Ovary half to totally inferior, with 2 locules. Style
elongating through the filament tube, stigma lobes 2, protruding and expanding
through the anther tube after the pollen has been shed. Fruits hemispherical
capsules, usually longitudinally ribbed, crowned by the persistent calyx lobes,
withered corolla, stamen tube, and style, longitudinally dehiscent by 2 apical
pores. Seeds oblong to oblong-elliptic, the surface yellowish brown, with
minute wrinkles or tubercles. About 365 species, nearly worldwide, most diverse
in tropical and warm temperate regions.
The pyridine alkaloid
lobeline is extracted from several species of Lobelia. This alkaloid is
similar to nicotine and has been used as an ingredient in antismoking
medications (Rosatti, 1986). Lobelia extracts have been used medicinally
to treat asthma and bronchitis, but in large doses they can cause nausea,
paralysis, and even death (Steyermark, 1963).