DEVELOPMENT OF PLANTS 443 



the pistils are reduced in number, ranging from two to more 

 commonly three or rarely five. Thus we see that the spiral 

 type of flower so often noticed in the rose and preceding orders 

 has become reduced as a rule to the cyclic type and that five 

 numerous sets of organs are not of common occurrence. This 

 reduction of the flower and the suppression of parts is well 

 illustrated in the maples (Fig. 318). The sepals cohere, forming 

 a five-lobed calyx. The petals are often suppressed and a 

 nectar disc is developed outside the stamens, a distinguishing 

 feature of the order (Fig. 318, C). The two whorls of stamens 

 are suppressed to a varying degree so that from four to eight 

 commonly appear and the pistils are normally reduced to two. 

 More frequently the flowers are imperfect, either the pistils or 

 stamens of each flower being aborted (Fig. 318, B). These two 

 kinds of imperfect flowers are arranged on the same or different 

 trees and they are adapted to small short-tongued lapping in- 

 sects which visit these open types of flowers. The intelligent 

 long-tongued bees and butterflies generally avoid such flowers, 

 having learned by experience with colors and odors that a surer 

 supply of food is to be found in those flowers that conceal their 

 nectar and so exclude the promiscuous crowd of insects that 

 swarm about the simpler types. It should be stated that the 

 development of imperfect or incomplete flowers appearing in 

 many of the orders is not to be looked upon as a primitive con- 

 dition, though common in the lower monocotyledons and dicoty- 

 ledons, since, throughout the Angiospermae, forms will constantly 

 appear in which one or another set of organs fails to develop. 

 The formation of anemophilous flowers, however, as in the box 

 maple, is a return to a primitive condition. 



The stimulation of fertilization results in a green wing-like 

 outgrowth on each of the ovaries that assists at first in the manu- 

 facture of food for the embryo and later becomes a dry, mem- 

 branous organ for seed distribution. This fruit, known as a 

 schizocarp or samar, is at first partly loosened from its support 

 and remains attached only by a small stalk (Fig. 319, B), which 

 requires a rather strong wind to snap it. Thus the fruit is 

 freed under conditions that will result in the widest dissemina- 



