172 THE HUMAN SIDE OF PLANTS 



Algae, there is no sex at all, and the entire plant is 

 but a single cell. This form of plant reproduces 

 by the simple method of cell-division : in some plants 

 the cell divides in the middle; in others, it bursts 

 open, producing a swarm of minute cells. In this 

 lower form there are no organs of reproduction. 



The next step in plant life is marriage between 

 members of the intermediate or confused sex, as 

 in certain pond-weeds. Here the plant cells are 

 precisely alike. 



But in the higher plants there are flowers, and 

 these flowers contain the organs of reproduction. 

 The flower is divided into various parts, including 

 stamen and pistil or male and female. In order 

 that the seeds may form and develop in the ovary 

 of the pistil, the beautiful grains of yellow pollen 

 must be brought from the stamens and showered 

 upon the tip of the pistil the stigma and from 

 there they are carried down the long style to the 

 ovary, where they quicken the tiny ovules. 



When we speak of flowers we rarely stop to 

 consider just what the term means! It means not 

 only the pistil, which contains the undeveloped 

 seeds or ovules; the stamens with their pollen 

 grains; but the petals, or, taken together, the co- 

 rolla; and lastly the calyx all these different parts 

 combine to form the flower. The brilliantly col- 



