294 HOW CROPS GROW. 
ingly, constitute a perfect flower even in the absence of 
calyx and corolla. 
The flower of buckwheat has no corolla, but a white or 
pinkish calyx. 
The grasses have flowers in which calyx and corolla are 
represented by scale-like leaves, which, as the plants ma- 
ture, become chaff. 
In various plants the stamens and pistils are borne in 
separate flowers. Such are called monecious plants, of 
which the birch and oak, maize, melon, squash, cucumber, 
and oftentimes the strawberry, are examples, 
In case of maize, the staminate flowers are the “tas- 
sels” at the summit of the stalk; the pistillate flowers 
are the young ears, the pistils themselves being the “ silk,” 
each fiber of which has an ovary at its base, that, if fer- 
tilized, developes to a kernel. 
Diccious plants are those which bear the staminate 
(male, or sterile) flowers and the pistillate (female, or fer- 
tile) flowers on different individuals; the willow tree, the 
hop-vine, and hemp, are of this kind. 
Fertilization and Fructification.—The grand function 
of the flower is fructification. For this purpose the pollen 
must fall upon or be carried by wind, insects, or other agen- 
cies, to the naked tip of the pistil. Thus situated, each 
pollen-grain sends out a slender tube of microscopic diam- 
eter, which penetrates the interior of the pistil until it en- 
ters the seed-sack and comes in contact with the ovule or 
rudimentary seed. This contact being established, the 
ovule is fertilized and begins to grow. Thenceforward 
the corolla and stamens usually wither, while the base of 
the pistil and the included ovules rapidly increase in size 
until the seeds are ripe, when the seed-vessel falls to the 
ground or else opens and releases its contents. 
Fig. 62 exhibits the process of fertilization as observed 
in a plant allied to buckwheat, viz., the Polygonum con- 
