1. Linaria vulgaris Mill. (butter and eggs)

Pl. 482 f, g; Map 2209

Plants perennial herbs (frequently flowering the first year), with fibrous roots, terrestrial. Stems 30–80 cm long, erect or ascending, glabrous below the inflorescence (this occasionally sparsely glandular-hairy). Leaves relatively dense, alternate or occasionally the lowermost leaves appearing opposite, sessile or very short-petiolate, the petiole bases not expanded. Leaf blades 2–7 cm long, 1.5–6.0 mm wide, linear, angled or slightly tapered to a sharply pointed tip, tapered at the base, unlobed, the margins entire, usually only a midvein apparent, glabrous. Inflorescences dense terminal spikelike racemes, the flower stalks 1–4 mm long at flowering, not becoming elongated at fruiting, each subtended by a linear to lanceolate bract (3–25 mm long); bractlets absent. Flowers perfect. Calyces 2.5–4.5 mm long, deeply 5-lobed nearly to the base, the lobes slightly unequal in length, lanceolate to narrowly ovate, sharply pointed at the tip, glabrous. Corollas 20–30 mm long (including the spur), bilabiate, 5-lobed, glabrous except for the bearded base of the lower lip, the tube shorter than to about as long as the lobes, light yellow with a darker yellow and orange throat, the tube with a straight or somewhat curved, slender spur 8–14 mm long at the base (this positioned between the lower 2 calyx lobes), the throat mostly closed by the strongly convex base of the lower lip, the upper lip more or less straight, strongly folded longitudinally between the 2 lobes, the lower lip with the lobes more or less recurved. Fertile stamens 4, the filaments of 2 lengths, not exserted, the anther sacs spreading; staminodes absent (but the lower lip bearded at the base). Style 1, not exserted, the stigma capitate, unlobed. Fruits capsules, 5–10 mm long, ovoid to more or less globose, glabrous, the 2 locules equal or unequal in size, each dehiscent from the tip by 3–5 teeth. Seeds numerous, 1.5–2.5 mm long, circular to broadly oblong-elliptic in profile, flattened and with a broad marginal wing, the surface black, the main body with scattered small warts or tubercles. 2n=12. May–November.

Introduced, scattered nearly throughout the state (native of Europe, Asia; introduced throughout temperate North America). Ditches, fallow fields, pastures, fencerows, cemeteries, old homesites, gardens, railroads, roadsides, and open, disturbed areas.

Butter and eggs is an attractive ornamental, but is considered to be a significant invader of native plant communities in some states. In 1742, a young Swedish botanist brought to the attention of Carolus Linnaeus an abnormal form of Linaria vulgaris that he had discovered while botanizing near Uppsala. In this plant, the flowers were actinomorphic and 5-spurred rather than the usual condition of a zygomorphic corolla with a single spur. Although he recognized it as an unusual kind of Linaria, Linnaeus was unable to account for this developmental abnormality and subsequently named it as a new genus Peloria (derived from the Greek, for monster). The phenomenon of developmental monstrosities that affect floral symmetry has since become known as pelorism (Å. Gustafsson, 1979) and is known from several other species, including Antirrhinum majus. Linaria vulgaris has been an important research tool in the study of the developmental biology of flowers, mutations that affect flower morphology, and the inheritance of genes that affect floral development (Meyerowitz et al., 1989).