MODIFICATIONS OF ORGANS. 111 
ment of nectar—as baits for different kinds of insects, are 
usually closely associated with special forms of the stamens 
and pistil, and have relation to the mode of fertilisation of 
er. 
bs White the majority of flowering plants bear hermaphrodite 
flowers—i.e., those containing both stamens and pistil—it is 
very commonly the case that fertilisation of the ovules is 
only accomplished when pollen from a different plant of the 
same species is brought to the stigma. Many hermaphrodite 
flowers are quite capable of self-fertilisation, but appear to 
benefit by crossing, the resulting seeds usually producing very 
fine and strong plants. It has further been shown that, even 
among such plants, pollen from others of the same species 
appears to have a more powerful fertilising action on the 
stigma than other pollen from the same flower has, even when 
the latter has been applied first. In alarge number of species 
the pollen is not capable of fertilising the flowers from which 
it is taken, and in these cases cross-fertilisation must take 
place. And, as if to insure that self-fertilisation will not 
occur, numerous contrivances have arisen to render it difficult 
or all but impossible. ‘These have been already referred to in 
detail, and need only be mentioned again here. Among these 
contrivances: are (1) the more or less complete separation of 
the essential organs in moncecious and dicecious plants; 
(2) dichogamy, or the maturing of the anthers and stigmas at 
different times ; and (8) heterostylism, or the unequal lengths 
of stamens and styles; besides innumerable individual modi- 
fications of structure, all tending in the same direction. In 
violets—and no doubt in many other plants—we see adapta- 
tions for producing seed by self-fertilisation in cleistogamic 
flowers, in addition to those seeds which are produced by 
crossing in the ordinary flowers of the plant. 
The modifications of the fruit are chiefly in the direction 
of insuring distribution of the seeds. The chief agencies 
which are taken advantage of in this work are those of water, 
wind, and animals, besides which a few plants have acquired 
the power of scattering their seeds more or less perfectly by 
some mechanical contrivance. 
Water, particularly in running streams, serves to carry 
many fruits and seeds from higher to lower levels, and these 
frequently become stranded, and germinate. But, with the 
exception of a few aquatic or semi-aquatic plants, there are 
very few which have become specially modified to suit this 
mode of dissemination. One of these few is the Coconut, 
roe fruits can withstand soaking in sea-water for some 
months. 
Wind is a most efficient agent in scattering seeds. In 
