6. Collinsia Nutt.

Plants annual, with taproots, terrestrial. Stems erect or strongly ascending, sometimes from a spreading base, unbranched or branched, moderately to densely pubescent with minute, glandular hairs toward the tip, glabrous toward the base. Leaves opposite, the uppermost sessile and clasping the stem, grading into the lower, short- to long-petiolate ones. Leaf blades simple, unlobed, variously lanceolate to oblong, elliptic, or ovate (those of the lowermost leaves sometimes broadly ovate to nearly circular), rounded or bluntly to sharply pointed at the tip, the margins otherwise entire to shallowly scalloped or toothed, the surfaces glabrous or sparsely and minutely hairy toward the base of the midvein, the venation pinnate, but the lateral veins sometimes very faint. Inflorescences terminal racemes, but often appearing axillary because of the pair of leaflike bracts at each node, the flowers opposite or whorled at the nodes, long-stalked; bractlets absent. Flowers perfect. Calyces somewhat irregularly 5-lobed to below the midpoint, bell-shaped, nearly actinomorphic but oriented slightly obliquely, the lobes narrowly lanceolate to lanceolate, sharply pointed at the tip, glabrous except sometimes minutely hairy along the margins, often pinkish- or purplish-tinged. Corollas bilabiate, 5-lobed, glabrous or the tube sparsely hairy, the upper lip 2-lobed, angled upward to recurved, white (occasionally faintly bluish- or purplish-tinged), the lower lip 3-lobed, purple or blue to purplish blue (sometimes grading to white basally or with a white central line on each lateral lobe, rarely entirely white), the lateral lobes arched somewhat downward to nearly straight, the central lobe shorter and folded lengthwise (enclosing the stamens and style), partially obscured by the lateral lobes, the tube shorter than the lobes, white or pale purplish- or bluish-tinged, lacking a spur, but slightly swollen or pouched on the upper side above the base, the throat closed by the convex or ridged base of the upper lip, often with yellow to brownish yellow mottling or spots on the upper side. Fertile stamens 4, the filaments of 2 lengths, hidden in the folded lowermost lobe, the anther sacs spreading, confluent at their tips; staminodes absent or more commonly 1 present as a short knoblike or ribbonlike structure. Style 1, hidden in the folded lowermost lobe, unbranched, the stigma small, capitate, unlobed or shallowly 2-lobed. Fruits capsules, more or less globose, circular in cross-section, glabrous, the 2 locules equal in size, dehiscent longitudinally along and between the 2 sutures. Seeds 2 to numerous, somewhat asymmetrically broadly oblong-ellipsoid to ovoid, more strongly convex on 1 side than on the other, the surface dark brown, with a minute and sometimes faint network of fine ridges in longitudinal rows (this often visible only with strong magnification). About 20 species, North America.

The genus Collinsia is most diverse in the western states, especially California. Our species are both winter annuals with seeds that germinate during the autumn, producing flowering stems the following spring and dying soon after the fruits mature. Pennell noted the structural similarities of the corollas to the papilionaceous flowers of many members of the legume family Fabaceae. He reviewed the floral adaptions to bee pollination, in which the weight of the landing insect causes the boat-shaped central lobe of the lower lip to spread, making the pollen accessible and bringing the anthers and stigma into contact with the lower abdomen of the insect.

Some species of Collinsia are prized for their attractive 2-colored corollas and are cultivated in sunny garden beds and in rock gardens. In Missouri, the species most-often grown is C. verna, which usually seeds itself readily. Steyermark (1963) noted that during his time populations of C. violacea frequently formed dense, showy patches along some roadsides in southwestern Missouri, but this is not usually the case today. However, C. verna is a conspicuous wildflower in some rich ravines and valleys, forming colorful carpets of blue and white.