Corolla

[Lat. corolla; dim. of corona, a crown; Fr. corolle.] ( Bot.) The inner envelope of the flower, consisting of leafy organs called petals, and situated, in a complete flower, between the calyx and the stamens. It is generally the most conspicuous whorl of organs, being more or le colored. It is, in fact, that part of the plant which usually delights us most by its gay appearance and fragrance. Petals are rarely green, though occasionally this color is met with, as in some Cobæas, in Hoya virid i flora, Go no lobus virid i flor us, and Pentatro pis spiral is. When there is but one whorl of enveloping organs in the flower, it is regarded as the calyx (which see), and the flower is said to be a petaloid. A petal is often narrowed below into a stalk-like portion analogous to the petiole of a leaf, as in the wall-flower; the narrowed portion is then termed the unguis or claw, and the expanded portion the limb. Such a petal is said to be unguiculate or clawed. The shapes of petals are indicated in botanical descriptions by terms easily understood; such as oblong, lanceolate, elliptic, orbicular, ovate, and cordate, applied to the outlines; and concave, tubular, and boat - shaped, applied to the forms of petals which are not flat. In describing their direction, the terms erect, connivent, divergent, and reflexed, are used in the same sense as when applied to the parts of the calyx. The petals, like the sepals, may be either distinct, or more or le united into one body. In the former case, the C. is said to be polypetalous or dialypetalous; in the latter, monopetalous or gamopetalous. The number of petals in a polypetalous C. is indicated by a prefix, as in the case of a polypetalous calyx; thus a C. of two petals is said to be dipetalous; of three, tripetalous; of four, tetra petalous, and so on. When the petals are all of the same size and form, the C. is termed regular; when they vary in these particulars, it is said to be ir regular. We give below the more important forms of the regular poly petal ous C.:-Cruciform , consisting of four petals, usually with claws, as in the wall-flower (fig. 693, in which two of the petals are turned back to show the claws); but sometimes without claws, as in the Celandine, and the whole arranged in the form of a cro . Caryophyllace ous,-consisting of five petals with long claws inclosed in the tube of the calyx, and with their limbs commonly Fig. 693. - CRUCIFORM COROLLA. placed at right angles to the claws, as in the Lychnis, Single pink, Carnation, and Catch-fly. Rosaceous , composed of five petals, without, or with very short claws, and spreading in a regular manner, as in the Strawberry and Single rose. There are many anomalous forms of the irregular polypetalous C., to which no particular names are applied. There is one form, however, of great importance, namely, the Papilio mace ous . (Fig. 65.) This derives its name from the fancied resemblance which it bears to a butterfly ( papilio ). It is composed of five petals, one of which is superior and larger than the others, and is termed the standard or vexillum ; two are inferior, and usually more or le united, so as to form a somewhat boat-shaped cavity, called the keel or carina ; and two are lateral, and termed the wings or ala . This curious form is common to the various species of the Pea, and a vast number of plants which form the sub-ord. Papili onacer of the Leguminosa. When the petals unite, so as to form a monopetalous C., various terms are used, as in the case of the monosepalous calyx, to indicate the degree of adhesion; such as partite , cleft , toothed , and entire. (See CALYX.) The part where the union bas taken place is called the tube ; the free portion, the limb ; and the orifice of the tube, the throat or faux . The monopetalous is regular when the parts are of the same size and form, and united so as to form a symmetrical body; it is irregular when these conditions are not complied with. The most noteworthy forms of the regular monopetalous C. are distinguished as follows: -Tubular , - nearly cylindrical throughout, as in the central florets of many composite plants, like the Ragwort, Chrysanthemum, and Milfoil. Campanulate , or bell -shaped, rounded at the base, and gradually enlarging to the summit; as in the Harebell, (fig. 492.) Infundibuli form , or funnel - shaped ; as in Convolvulus and Tobacco. Hypo crateriform, or salver -shaped, - the tube long and narrow, and the limb at right angles to it; as in Phlox, Auricula, and Primrose. Rotate, or wheel-shaped, tube short, otherwise similar to the preceding form; as IMG:content-0377.png:[blocks in formation] This form is common to most of the plants in a, calyx; b, corolla. IMG:content-0378.png:[blocks in formation]