SPERMATOPHYTA 



373 



vestiges. The two kinds of flowers may occur on the same plant (monoe- 

 cious condition) or on separate plants (dioecious condition). 



The Perianth. In a typical flower the perianth consists of two differen- 

 tiated sets of parts, the outer set being the calyx and the inner set the 



stamen 



receptacle 



Fig. 318. Floral structure of the large-flowered trillium {Trillium grandiflorum) . A, a 

 single flower, two-thirds natural size; B, four of the stamens and the pistil, twice natural 

 size; C, cross section of the ovary, the dotted lines indicating the junction of the carpels, 

 X 10; D, the floral diagram. 



corolla (Fig. 318). The calyx is made up of sepals, the corolla of petals. 

 Ordinarily the sepals are scale-like and green, while the petals are larger 

 and either white or of some other color than green. Both may be small 

 and inconspicuous, however, as in the rushes {J uncus), or large and 

 showy, as in the lilies {Lilium) . In some flowers the perianth consists of a 

 single set of parts. These may be greenish and scale-like, as in the beet 

 {Beta), or large and showy, as in the anemone. In either case the flower 

 is said to be apetalous and the single whorl is arbitrarily designated as the 

 calyx. This is based on the assumption that the corolla is the missing 



