INTRODUCTION 
sometimes single below but divided above, as in most Composite , in which 
it bifurcates, and in Iris in which it separates into three flattened or 
petaloid portions. In Primroses, Wood-sorrel, Flax, Purple Loosestrife, and 
some other cases, there is a remarkable variation in the relative lengths of 
stamens and styles in different individuals of the same species, known as 
heterogony , the pollen from any stamen being found to be prepotent , i.e. to 
germinate sooner, upon the stigma of a style of the same length, which 
will only occur on a different individual. As anther and stigma of parts 
of equal length will obviously touch the same part of the body of any 
visiting insect, this is an adaptation to secure cross-pollination. 
The stigma may be a line of receptive surface sticky with a sugary 
secretion, as on the inner surface of the Y-shaped style in Composite t, or it 
may be nearly spherical, as in the Primrose. In plants pollinated by wind, 
such as Grasses and Salad-Burnet, it is a feathery plume-like structure. 
When the pollen reaches the stigma and begins to germinate, or send 
out its slender pollen-tubes, which are, of course, microscopic, down 
through the style into the ovary, and so to the ovules, the perianth 
generally withers, and corolla, stamens, and sometimes sepals, fall off, 
while the ovary, and the ovules it contains, enlarge. In some Orchids it 
is not until pollination that the ovules make their first appearance on 
the placenta. 
The number of ovules varies from one or two in each chamber of the 
ovary up to several hundred ; but some of them often fail to develop, so 
that, though each seed has been an ovule, the number of 
seeds in a fruit by no means necessarily agrees with the 
number of ovules there were in the ovary. The ovule is known as a seed 
from the moment when the pollen-tube has entered it so as to fertilise 
it or “ set the seed.” 
The fruit is formed of the ovary and any other adherent parts of a 
flower that persist after this fertilisation. Among existing plants it is only 
in a comparatively small number, represented here by the 
Pine, the Juniper, and the Yew, that the ovule is not 
enclosed in an ovary. These plants, all of which are woody, are known as 
Ovules 
Fruit 
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