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184 Structural and Physiological Botany. | 
carried to the stigma, either by the wind! [avemophzlous|, or 
by the agency of insects [eztomophilous|, or by peculiar 
movements (see pp. 203, 205) of the stamens or carpels, 
and remain attached to it in consequence of its exuding a 
_ viscid fluid. If we consider the immense number of pcllen- 
grains produced in any individual flower, and in addition 
the fact that a single one of these grains suffices for the fer- 
tilisation of an ovule, it would appear at first sight as if 
ample provision were made in the majority of plants for 
this first act in the process of fertilisation, especially if at-. 
tention is directed to the relative positions of the anthers 
and stigma. ‘Thus, for example, in most plants with pen- 
dent flowers, such as the fuchsia, the anthers are always 
placed higher than the long-styled stigma, so that in the act 
of pollination, that is, the dispersal of the pollen, some pollen- 
grains must almost inevitably become attached to the 
stigma. But in spite of the frequent occurrence of such 
favourable arrangements, there are many cases in which 
fertilisation is impossible without foreign aid, as in the Or- 
‘chideze and Asclepiadeze (Fig. 355 E), in which the pollen- 
grains are firmly united together by a viscid substance into 
a mass, and he undisturbed in the open anthers. In 
these cases assistance is given by the host of insects which, 
in their search for honey, fly busily from flower to flower, 
penetrate to the nectaries, and unintentionally and unknow- 
-ingly carry the fertilising pollen from one flower to another. 
In a large number of flowers, as, for instance, the Legumi- 
nose, other contrivances are also found, by means of which 
the pollen is conveyed to particular parts of the bodies of 
the insects in their search for honey, vz. to those which 
“must come into contact with the stigma when the insect 
visits the next flower. And since the majority of insects 
1 In forests consisting of those trees which bear catkins (Amen- 
tiferze) immense clouds of pollen are often seen floating in the air at 
the time of pollination, which are sometimes carried to the earth by 
showers of rain, and then form the so-called ‘sulphur-rain.’ 
Rashes <= 
—. 
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