Fig. 577.—Marrubium vulgare.
c. Strongly bilabiate calyx, the lips closing together after flowering.—Scutellaria (Skull-cap); the two lips of the calyx are entire, the upper lip has a large spur, and drops off on the ripening of the fruit. The flowers are generally solitary and turned to one side.—Prunella (Heal-all); the calyx is compressed, its two lips are strongly dentate, the upper lips closing slightly round the under. The stamens have a tooth-like projection beneath the anthers.
3. Nepeteæ, Catmint Group. 13–15 nerves in the calyx; this deviates from the other groups in the posterior stamens being the longer. The upper lip is slightly arched. Nepeta (Catmint), also Glechoma (Ground Ivy), with regular, and Dracocephalum with irregular calyx.
Fig. 578.—Mentha aquatica, var. crispa.
4. Satureieæ, Mint Group. The upper lip is flat, most frequently ovate, or almost spherical, and emarginate (Fig. [578]). The calyx is most frequently 5–10-nerved. 4 stamens, the anterior being the longer; rarely, 2 stamens only.—Mentha (Mint, Fig. [578]) has a regular, 5-dentate calyx, a small, almost regular, 4-partite corolla, and 4 erect stamens of nearly equal size. The verticillasters are many-flowered, and are often collected into cylindrical inflorescences. Herbs.—Lycopus (Gipsy-wort); corolla almost regular. 2 stamens, the posterior lateral ones are wanting. Preslia: 4-dentate calyx, 4-partite, regular corolla; 4 stamens of equal size.—Thymus (Thyme, Fig. [575]) has a strongly bilabiate calyx, the throat being closed by a whorl of hairs (Fig. [575] B). The corolla is distinctly labiate. Under-shrubs, with small entire leaves; verticillasters few-flowered and separate.—Origanum (Marjoram); spike or capitate inflorescences with the flowers solitary in the axils of the rather large and distinctly 4-rowed (often slightly coloured) floral-leaves. Melissa. Calamintha. Clinopodium (Wild Basil). Satureia. Hyssopus (Hyssop); small, entire leaves; the verticillasters are situated unilaterally in a slender, spike-like inflorescence. Lavandula (Lavender); shrubs with verticillasters collected in cylindrical, long-stalked inflorescences; the calyx is tubular, has 13–15 nerves, the posterior tooth is much larger than the others. Stamens and style do not project. Coleus differs, among other characters, in having united filaments; the stamens and style are bent down and concealed in the boat-shaped under lip.
Fig. 579.—Salvia officinalis.
5. Monardeæ, Salvia Group. Only the 2 anterior stamens are developed.—Salvia (Fig. [579]); calyx deeply bilabiate; the upper lip of the corolla is generally strongly compressed. Rudiments of the two lateral stamens are present. The connective in the two fertile stamens is long and filamentous, and bears at the upper end a normal half-anther, but at the lower one a barren, often broader portion, against which the insect is obliged to push its proboscis during its visits to the flowers, causing the pollen-bearing half-anther to be pressed down against its back. Floral-leaves often coloured.—Rosmarinus (Rosemary); a shrub with leathery linear leaves, with rolled back edge. A small tooth on the filament represents the barren half of the anther. Monarda.
The POLLINATION is generally effected by insects, especially bees; the under-lip is the landing-stage and the pollen is deposited on their backs. Cross-fertilisation is promoted by dichogamy; honey is secreted by an hypogynous disc and collected in the corolla-tube. Some genera are homogamous (Lamium, Galeopsis, etc.); others are dichogamous (protandrous); a few are gynodiœcious: ♀-and ☿-flowers in various relative sizes (Glechoma hederaceum, Thymus, Salvia pratensis, and others). The entrance of uninvited guests to the honey is often rendered difficult by whorls of hairs, etc. In numerous instances the upper lip protects the pollen from rain. Cleistogamy is found e.g. in Lamium amplexicaule.