THE FLOWER OF THE HIGHER SEED-PLANTS 149 
following one, and all the members of each whorl are alike 
(Fig. 98). 
176. Suppression and Multiplication of Whorls. — Any 
whorl or part of a whorl may be suppressed. If one set of 
parts of the perianth is lacking, this is 
assumed to be the corolla and the 
flower is said to be apetalous (Fig. 99). 
Multiplication of whorls is particu- 
larly frequent among the stamens, but 
other whorls may also show it (see 
Figs. 117, 118). 
177. Unisexual Flowers. — The sta- ca 
mens and pistils may be produced in ves ce 
separate flowers, which are uniserual wild Ginger. 
(often called imperfect) flowers. In the : 
very simple unisexual flowers of the willow (Fig. 100) each 
flower of the catkin (Appendix I, Fig. 6) consists merely 
of a pistil or a group of (usually two) stamens springing 
from the axil of a small bract. 
Staminate and pistillate 
flowers may be borne on dif- 
ferent plants, as they are in 
the willow, or they may be 
borne on the same plant, as 
in the castor-oil plant, Indian. 
corn, and the begonias. When 
staminate and pistillate flow- 
Fic. 100. Flowers of Willow. ers are borne on separate 
(Magnified.) plants, such a plant is said 
A, staminate flower; B, pistillate 45 be diecious (of two house- 
re holds); when both kinds of 
flower appear on the same individual, the plant is said to 
be monecious (of one household). 
