Corolla

Corolla, the inner floral envelope or whorl of the perianth, which is generally of a delicate or "petaloid" texture and white or coloured, serving, at least in many cases, to attract insects (or more rarely birds) and so secure the cross-pollination (q.v.) of the flower. It may also be scented. The leaves of the corolla, which are called petals, have commonly a narrow base, simple outline, entire margin and broad obtuse apex, being sometimes distinguished, as in the wallflower, into a claw and limb or blade; but they may be notched, as in chickweed, fringed, as in pinks, or torn (laciniate), as in the ragged robin. They are generally three in number among Monocotyledons, and five among Dicotyledons; but in cultivation many flowers become "double" by the replacement of some of their stamens by additional petals. The petals may be distinct (polypetalous) or coherent, from intercalary growth carrying them up on a tube (gamopetalous); and they may spring from below the ovary (hypogynous), in a ring round it (perigynous), or from the top of it (epigynous). These characters are of primary importance in classification. The corolla may be polysymmetric, as in the rosaceous, caryophyllaceous, and cruciform types among Polypetalae, and in the tubular, campanulate, urceolate, funnel-shaped, salver-shaped and rotate types among Gamopetalae; or it may be monosymmetric, as in the papilionaceous, bilabiate and ligulate types. Flowers that are habitually self-pollinated have commonly white, uniformly-coloured or inconspicuous corollas: those adapted to insect fertilisation (q.v.), besides being conspicuously coloured, are often marked by dots or lines known as honey-guides and often themselves secrete honey. In the bud the petals are variously folded, and in duration they may be caducous, as in the vine, falling as the flower opens; deciduous, falling after fertilisation; or, though rarely, persistent, as in Campanula.