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 In like manner, the corolla may be composed of petals, or it may be of one piece and variously lobed. A calyx of one piece, no matter how deeply lobed, is gamosepalous. A corolla of one piece is gamopetalous. When these series are of separate pieces, as in Fig. 173, the flower is said to be polysepalous and polypetalous. Sometimes both series are of separate parts, and sometimes only one of them is so formed.

The floral envelopes are homologous with leaves. Sepals and petals, at least when more than three or five, are in more than one whorl, and one whorl stands below another so that the parts overlap. They are borne on the expanded or thickened end of the flower stalk; this end is the torus. In Fig. 173 all the parts are seen as attached to the torus. This part is sometimes called the receptacle, but this word is a common-language term of several meanings, whereas torus has no other meaning. Sometimes one part is attached to another part, as in the fuchsia (Fig. 174), in which the petals are borne on the calyx-tube.

Subtending Parts.—Sometimes there are leaf-like parts just below the calyx, looking like a second calyx. Such parts accompany the carnation flower. These parts are bracts (bracts are small specialized leaves); and they form an involucre. We must be careful that we do not mistake them for true flower parts. Sometimes the bracts are large and petal-like, as in the great white blooms of the