Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/143

Rh COROLLA.] B T A N Y 133 adhere by the apices. When the petals are equal as regards their development and size, the corolla is regular ; when unequal, it is irreynlar. When a corolla is gamopctalous, it usually happens that the claws are united into a tube, while the upper parts are either free or partially united, so as to form a common limb, the point of union of the two portions being the faux or throat, which often exhibits a distinct constriction or dilatation. The number of parts forming such a corolla can be determined by the divisions, whether existing as teeth, crenations, fissures, or partitions, or if, as rarely happens, the corolla is entire, by the vena tion The union may be equal among the parts, or some may unite more than others. Amongst regular polypetalous corollas may be noticed the rosaceous corolla (fig 206), in which there are five spreading petals, having no claws, and arranged as in the single Rose and Potentilla ; the caryophyllaceous corolla, in which there are five petals with long narrow tapering claws, as in many of the Pink tribe ; the alsinaceous, where the claw is less narrow, and there are distinct spaces between the petals, as in some species of Chickweed ; the cruciform, having four petals, often unguiculate, placed opposite in the form of a cross, as seen in Wallflower, and in other plants called cruciferous. Of irregular polypetalous corollas the most marked is the papilionaceous (fig. 187), in which there are five petals : one superior (posterior), st, placed next to the axis, usually larger than the rest, called the vcxillum or standard; two lateral, a, the ake or wings; two inferior (anterior), partially or completely covered by the alre, and often united slightly by their lower margins, so as to form a single keel-like piece, car, called carina or keel, which em braces the essential organs. This form of corolla is charac teristic of British Leguminous plants. Among the irregular polypetalous corollas might be included the orchideous (fig. 207), although it is really the perianth of a Mono cotyledon. This perianth consists of three outer portions equivalent to the calyx, and three inner parts alternating with them, constituting the petals. The latter are often very irregular, some being spurred, others hooded, &c.; and there is always one, called the labdlum or lip I, which presents a remarkable development, and gives rise to many of the anomalous forms exhibited bv these flowers. Fi&amp;lt;r. 206 Fi;,. 203. Fig. 207. FIG. 20G. Rosaceous corolla of thj Strawoerry (Fragnria ve&ea), composed of five petals without claws Fir,. 207. Flower of Twayblade (Lutera ovnt/tj, seen in front, showing a large bifid labellum /, which is different from the other five divisions of the perianth. The divisions of the perianth are in two rows of three each. The essential organs of reproduction are placed on a column opposite the labellum. Hie perianth is irregular polyphyllous, and is denominated orchideous. Fin. 208. Regular gamopetalous bell-shaped (ciunpanulate) corolla of Harebell (Campanula rotiindifo ia). It is composed of five pctala united The ovary is inferior, and is united to the calyx c Regular gamopetalous corollas are sometimes campanulate or bell-shaped, as in Campanula rotundifolia (fig. 208) ; tnfundibuliform or funnel-shaped, when the tube is like an inverted cone, and the limb becomes more expanded at the apex, as in Tobacco ; kypocraterfform or salver-shaped, when there is a straight tube surmounted by a flat spreading limb, as in Primula (fig. 209) ; tubular, having a long cylindrical tube, appearing continuous with the limb, as in Spigelia and Comfrey ; rotate or wheel-shaped t when the tube is very short, and the limb flat and spreading, as in Myosotis (when the divisions of the rotate corolla are very acute, as in Galium, it is sometimes called stellate or star- like) ; urceolate or urn-shaped, when there is scarcely any limb, and the tube is narrow at both ends, and expanded in the middle, as in Bell-heath (Erica cinerea). Some of these forms may become irregular in consequence of certain parts being more developed than others. Thus, in Ve ronica, the rotate corolla has one division much smaller than the rest, and in Digitalis there is a slightly irregular campanulate corolla which some have called digitaliform. Plate XI. Of irregular gamopetalous corollas there may be mentioned the labiate or lipped (fig. 210), having two divisions of the limb in the form of what are called labia or lips (the upper one, u, composed usually of two united petals, and the lower, I, of three), separated by a hiatus or gap. In such cases the tube varies in length, and the parts in their union follow the reverse order of what occurs in the calyx, where two sepals are united in the lower lip, and three in the upper. When the upper lip of a labiate corolla is much arched, and the lips separated by a distinct gap, it is called ringent (fig. 210). The labiate corolla characterizes the Fig. 209. Fig. 210. Fig. 211. FIG. 209. Regular gamopetalous sympetalous hypocrateriform corolla of Oxlip (I riinulaelatior). e, calyx; p, corolla; f, tube of corolla ; /, limb; a, anthers. FIG. 210. Irregular gamopetalous labiate corolla of the Dead-nettle (Lamium album). The upper lip is composed of two petals united, the lower lip /, of three. Between the two lips (labia) there is a gap (hiatus). The throat is the part where the tube and the labiate limb join. From the arching of the upper lip this corolla is called ringent. FIG. 211. Irregular gamopetalous ligulate flower of Ragwort (FentcU). It is a tubular floret, split down on one side, with the united petals forming a strap- like projection I. The linos on the flat portion indicate the divisions of the five petals. From the tubular portion below, the bitid style projects slightly. The terete fruit (achsenium) a is surmounted by pilose pappus, which is the metamorphosed calycine limb The flower is female, having no stamens. natural order Labiatse. When the lower lip is pressed against the upper, so as to leave only a chink or rictus between them, the corolla is said to be personate or mask- like, as in Frogsmouth, Snapdragon, and some other Scrophulariacere, and the projecting portion of the lower lip is called the palate. In some corollas the two lips become hollowed out in a remarkable manner, as in Calceolaria, assuming a slipper-like appearance, similar to what occurs in the labellum of some Orchids, as Cypri- pedium. The calceohtte corolla of Calceolaria may be con sidered as consisting of two slipper-like lips. When a tubular corolla is split in such a way as to form a strap-like process on one side with several tooth-like projections at its apex, it becomes ligulate, or strap-shaped (fig. 211).