134 



PLANT BIOLOGY 



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 ho- 

 mologous 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 re- 

 ceptacle, 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 



FIG. 174. FLOWER OF 

 FUCHSIA IN SECTION. 



