THE MEANING OE THE EEOWER 
59 
cell must be touched and wakened by another cell, and for 
flowers this other cell is contained in the pollen of another 
flower of its own kind. And so: 
The flower cell knows its time has come when the 
pollen touches it. 
Tet us examine a buttercup, and see how the whole 
flower is designed for this business of pollen shedding 
and pollen receiving, this business called pollination. 
On the outside are five or 
more green scales, like leaves. 
They form the calyx, which pro¬ 
tects the fragile inner parts of 
the bud, and, as the bud opens, 
steadies the flower. Next come 
Buttercup Cut in Half 
the bright yellow^ petals of the 
corolla, and inside the corolla are the pollen-bearing 
stamens. In each stamen the pollen is held in a sac at 
the end of a stalk; the sac is called the head, or anther. 
In the center of the flower are many small green grains, 
the carpels, and in each carpel is an ovule containing 
an egg-cell. The part of the carpels containing the ovule 
is called the ovary, or seed-vessel, because it is the ovules 
which will one day, when the pollen reaches them, become 
seeds. 
It is puzzling, after one has learned from a buttercup 
the four parts of the flower,—calyx, corolla, stamens 
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