20 FRUIT AND SEED. 
(fig. 32, sti), or it is situated on a stalk-like portion prolonged 
from the ovary, called the style (jig. 31, sty). The only essential 
parts of the carpel are the ovary and stigma; the style being no 
more necessary to it than the filament is to the stamen. 
The andreecium and gyncecium are called essential organs 
because the action of both is necessary for the production of the 
seed. It frequently happens, however, that either the gynoecium 
or androecium is absent from a flower, as in the Willow (figs. 34 
and 35), in which case the flower is termed wnisexual; and it is 
then still further characterised as staminate or male (fig. 34), or 
pistillate, carpellary, or female ( fig. 35), according as it possesses 
one or the other of these organs. 
Fig. 34. Staminate flowers of a species of Willow 
(Salix), —— Fig. 35, Pistillate or carpellary 
flowers of the same, 
ce. The Fruit and Seed.—Ata certain period the anther opens 
(fig. 27, a), and discharges the pollen, p, which is then carried 
to the stigma by insects, or borne by the wind; this is called 
pollination, and is the first step in the process which subse- 
quently takes place, which is properly termed fertilisation, and 
which consists in the commingling of the fovilla or male fertilising 
element of the pollen with the female element of the ovule—the 
oosphere. After fertilisation has been effected, important changes 
take place in the pistil and surrounding organs of the flower, the 
result being the formation of the fruit, which consists essenti- 
ally of the mature ovary or ovaries, containing the impregnated 
or fertilised ovule or ovules, then termed seeds. But in some 
cases, besides the mature ovary or ovaries, other parts of the 
flower, and even the peduncle, as will be explained hereafter 
when describing the fruit in detail, also become a part of 
the fruit. The fruit, when perfectly formed, whatever be 
its composition, consists of two parts: namely, the shell or 
os ss 
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