Stem. - Square, usually one or two feet high. Leaves. - Opposite, oblong, lance-shaped or linear. Flowers. - Blue. Calyx. - Two-lipped, the upper lip with a small, helmet-like appendage which at once identifies this genus. Corolla. - Two-lipped, the upper lip arched, the lateral lobes mostly connected with the upper lip, the lower lip spreading and notched at the apex. Stamens. - Four, in pairs. Pistil. - One, with a two-lobed style.

The prettiest and most striking of this genus is the larger skull-cap, S. integrifolia, whose bright blue flowers are about one inch long, growing in terminal racemes. In June and July they may be found among the long grass of the roadsides and meadows. They are easily identified by the curious little appendage on the upper part of the calyx, which gives to this genus its common name.

Perhaps the best-known member of the group is the mad-dog skull-cap, S. lateriflora, which delights in wet places, bearing small, inconspicuous flowers in one-sided racemes. This plant is quite smooth, while that of S. integrifolia is rather downy. It was formerly believed to be a sure cure for hydrophobia.

S. galericulata is usually found somewhat northward. Its flowers are much larger than those of S. lateriflora, but smaller than those of S. integrifolia. They grow singly from the axils of the upper leaves.