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 
Fie. 141. — Irregular Corolla of 
Sweet Pea. 
A, side view ; B, front view ; s, stand- 
ard ; ww, wings; k, 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 
