. Phacelia
Juss. (scorpionweed, phacelia)
Plants annual or
biennial (perennial elsewhere), with slender taproots (sometimes stouter in P.
bipinnatifida). Stems loosely to strongly ascending, sometimes from a
spreading base, variously pubescent, at least in part with stiff, straight,
spreading to downward-angled, somewhat pustular-based hairs, in some species
nearly glabrous with age. Basal leaves usually present (in some species the
oval, unlobed cotyledons also persistent) but often withered at flowering, usually
relatively small (the blade usually less than 7 cm long, except in P.
bipinnatifida), long-petiolate, the blade pinnately lobed or compound, the
upper surface usually not mottled. Stem leaves alternate, long-petiolate to
sessile, variously hairy. Leaf blades variously shaped, moderately to deeply
pinnately lobed or compound (entire elsewhere); the pinnae or lobes narrowly
rounded to more commonly bluntly or sharply pointed at the tip, the margins
otherwise entire to deeply lobed, the surfaces variously hairy. Inflorescences
initially sometimes compact, continuing to elongate during the flowering season
(except occasionally in P. covillei and P. ranunculacea),
consisting of solitary or less commonly paired open racemes with the flowers
often mostly oriented along 1 side, often somewhat congested and scorpioid at
the tip, the flower stalks 3–14 mm long at flowering, becoming elongated at
fruiting, variously hairy. Calyces becoming somewhat enlarged at fruiting,
lacking appendages, the lobes narrowly triangular to narrowly lanceolate
(sometimes becoming slightly broader at fruiting), sharply pointed at the tip,
the surfaces and margins variously hairy. Corollas narrowly to broadly
bell-shaped (sometimes nearly cylindrical in P. covilleii and P.
ranunculacea), white or lavender- or bluish-tinged. Stamens exserted or
not, the filaments attached at or near the base of the corolla tube, glabrous
or hairy, with a small linear gland between each pair of adjacent filament
bases, this usually fused along all or most of its length with a minute pair of
appendages or ridges. Ovary incompletely (sometimes nearly completely)
2-locular, the placenta-bearing portions of the wall intruding into the locule
as a partition. Style exserted or not, shallowly or deeply branched. Fruits
(2–)3–6 mm long, more or less globose, moderately to densely hairy toward the
tip, at least when young, 2–8-seeded. Seeds 1.5–3.0 mm long, ovoid with a
longitudinal line or ridge along the inner side to nearly globose, the surface
with a network of ridges or occasionally appearing pitted, brown or black. One
hundred fifty to 200 species, North America, Central America.
The Missouri
species of this genus have all been classified as members of subgenus Cosmanthus
(Nolte ex A. DC.) Constance, a group of about 15 species that is most diverse
in the eastern half of the United States (Constance, 1949b). However, more
taxonomic research is necessary to test whether the subdivision of the genus
into three subgeneric groups based primarily on cytological patterns and annual
vs. perennial habits reflects actual affinities (Sewell and Vincent, 2006).
Some species of Phacelia
cause dermatitis in a few individuals when handled, but this may be due to the
stiff sharply pointed hairs rather than because of reaction to some caustic
chemical exudate. The genus contains a number of species considered good bee
plants for the production of honey.