88 THE AMERICAN BOTANIST. 



reach the stigmas. Therefore, simple flowers have man}' 

 stamens and pistils. Since the stamens in such flowers 

 could not be arranged in a single whorl, we find them 

 placed spirally on the receptacle which is elongated to re- 

 ceive them. The stamens and pistils in the buttercup and 

 magnolia are arranged in spirals. The spiral arrange- 

 mentis most frequently noticed in stamens and pistils, but 

 it may occur in the other organs of the flower as in the 

 petals of the water-lil}-- or cactus. The higher flowers 

 have fewer stamens and pistils. These are usually ar- 

 ranged in circles and the flower is said to he cyclic. Evolu- 

 tion has proceded from spirals to cycles, and this reduction 

 of the essential organs has gone so far that the highest 

 types, though possessing five sepals, petals and stamens, 

 often have the pistils reduced to one. 



It is probable that the first flowers to possess petals 

 had these organs all alike and arranged radially as in the 

 buttercup, rose and lily. Later, the modifications of the 

 flower to protect the nectar from undesirable insect 

 visitors or to facilitate the work of cross-pollination, 

 made it "irregular," that is the petals began to be of 

 different shapes in the same flower. Thus was brought 

 about the two-lipped flowers of the mints, the butterfly- 

 like flowers of the pea family and the one-sided flow^ers of 

 violets, jewel-weeds and orchids. Plants with radiate 

 flowers are said to be actinomorphic, those with irregular 

 flowers zygomorphic. Evolution has, of course, proceded 

 from actinomorphic to z^'gomorphic flowers. 



It is not to be assumed that these various evolution- 

 ary^ forces have acted on all flowers in exactly the same 

 proportions. In one flower certain lines will be found ac- 

 centuated, in another very different ones. It is therefore a 

 never ending source of interest to the student to examine 

 the flowers in the light of these facts. Evolution seems 

 often to have proceded independently in each set of the 

 floral organs and one may find united pistils and separate 

 petals, or the reverse. 



