Fig. 575.—Thymus vulgaris.
The 142 genera are mainly distinguished according to the form of the calyx and corolla, the number, direction, and length of the stamens, the forms of the nuts, etc.
1. Ajugeæ, Bugle Group. Calyx 10-nerved; the upper lip is small; 4 stamens. The ovary is not so strongly lobed as in the following group, so that it is most nearly allied to the Verbenaceæ. The nuts are reticulately wrinkled. Ajuga (Bugle) has a very small upper lip. The upper lip of Teucrium (Germander) is deeply cleft, and the two lobes are bent on their respective sides towards the under lip, which in consequence appears to be 5-lobed, and the upper lip to be wanting.
Fig. 576.—Lamium album: A lateral view of flower; B longitudinal section; C ovary with nectaries (a); D the apex of the style; e, upper lip of corolla; c, b, c the three petals of the lower lip; f anthers; g stigma.
2. Stachydeæ, Betony Group. The calyx is 5- or 10-nerved. The upper lip of the corolla is most frequently strongly arched or helmet-shaped; 4 stamens, the anterior pair the longer (Fig. [576]).
a. A somewhat regular and 5–10-dentate calyx with projecting stamens.—Stachys (Betony, Woundwort); the lobes of the under lip are rounded off. The anterior filaments, after pollination, bend outwards. Betonica—Ballota (Horehound); the calyx is funnel-shaped, and has triangular, long, pointed, awn-like teeth.—Galeopsis (Hemp-nettle) has two conical protuberances on the under lip between the lateral and the central lobes. The anthers open by 2 unequal valves. Lamium (Dead-nettle, Fig. [576]) has dentate, lateral lobes on the under lip. L. album (White Dead-nettle), L. rubrum, etc. Galeobdolon.—Leonurus; Phlomis.
b. Tubular, regular, often 10-toothed calyx and concealed stamens.—Marrubium vulgare (Fig. [577]); 10 calyx-teeth, hooked at the apex; many almost spherical whorls of flowers in the axils of the foliage-leaves, at some distance from one another.—Sideritis.
