The polypetalous corolla, as well as the gamophyllous corolla, may be regular or irregular, according as the foliola are equally or unequally united. But here again we must be careful not to lay down too absolute rules. Examine, for instance, the gamophyllous corolla of the gentians; their two lobes are very unequal, and yet the corolla is regular: five very large lobes alternate with five very small, in such wise that each of the latter is situated between two larger lobes. Each division of the corolla of the periwinkle is irregular, and yet the aggregate of their divisions is regular: these are all of the same form and the same size. In the gamophyllous corolla we are able to discern, through the different forms it assumes, the form of the parts which compose the union. Thus, for example, the _tubulate_ corolla supposes the pre-existence of unguiculate petals. * * * * * Inequality of union produces the _bilabiate_ corolla, which is invariably tubular. This is the case in the natural family of the Labiatæ. The upper lip is composed of two petals, and the lower of three. The parts of the upper are sometimes so closely joined that they appear to be but one, as in the _Lamium_; and the lower often becomes quadrilobed by the division of the middle petal, as in the _Stæcha_. In the labiated corolla, the mouth of the tube is open, while in the _personate_ or _masked_ (_persona_, a mask) it is closed by the pressure of the lower lip against the upper; as in Snapdragon and Frogsmouth, the projection of the lower lip being called the _palate_. By this feature the family of the Scrophulariaceæ is easily distinguished from that of the Labiatæ. In some corollas, the two lips are hollowed out in a very singular fashion, as in the Calceolaria; assuming a "slipper-like appearance," similar to what takes place in the labellum of certain orchids,--to wit, the _Cypripedium_. These _calceolate_ (_calceolus_, a slipper) corollas may be looked upon as consisting of two slipper-like lips. * * * * * The forms of the bilabiate, tubular, and ligulose florets, of the capitula of the Synantheræ, are likewise due to simple differences of union. The floscular capitulum comprises the tubular florets, and the semi-floscular capitulum, the ligulate florets; the radiate capitulum consists of florets ligulate or bilabiate at the circumference, and of tubular florets over the rest of the receptacle. By considering the capitula, as the vulgar do, to be flowers, Tournefort introduced considerable confusion into the nomenclature of the Synantheræ. SUMMER FLOWERS. "Dawn, gentle flower, From the morning earth! We will gaze and wonder At thy wondrous birth! "Bloom, gentle flower, Lover of the light, Sought by wind and shower, Fondled by the night!"[61] THE PRUNELLA, OR SELF-HEAL. [Illustration: FIG. 48.--"Rejoicing in the shade of over-arching elms."]