STRUCTURE OF THE FLOWER AND ITS ORGANS 199 



are familiar examples of flowers which are unsymmet- 

 rical because they have a large, indefinite number of 

 stamens ; the portulaca is unsymmetrical, since it has two 

 divisions of the calyx, five or six petals, and seven to 

 twenty stamens. 



210. The Receptacle. The parts of the flower are 

 borne on an expansion of the peduncle, called the recep- 

 tacle. Usually, as in the flower of the grape (Fig. 250), 

 this is only a slight enlargement of the peduncle, but in 



FIG. 141. Irregular Corolla of 

 Sweet Pea. 



, side view ; B, front view ; s, stand- 

 ard ; w w, wings ; fc, keel. 



the lotus and the magnolia the receptacle is of great size, 

 particularly after the petals have fallen and the seed has 

 ripened. The receptacle of the rose (Fig. 142) is hollow, 

 and the pistils arise from its interior surface. 



211. Imperfect or Separated Flowers. The stamens 

 and pistils may be produced in separate flowers, which 

 are, of course, imperfect. This term does not imply that 

 such flowers do their work any less perfectly than others, 

 but only that they have not both kinds of essential organs. 

 In the very simple imperfect flowers of the willow (Fig. 

 143) each flower of the catkin (Fig. 131) consists merely 



