172 THE HUMAN SIDE OF PLANTS 
Alge, 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- 
