PHYSIOLOGY. 319 
like the two first, but as soon as it has risen, the 
two last come both at once. ‘To the second kind 
belong the horse chesnut, (Aesculus Hippocastanum), 
and others. 
But if in homogamic flowers the stamens are 
shorter than the pistil, the flower 1s pendulous, so 
that the pollen, when falling off, may be enabled 
to perform its functions. Rarely have such flowers 
an oblique or horizontal position, and in this case 
the style turns backwards, to reach the stamens. 
Some pendulous flowers, however, can only be fe- 
cundated by insects, as their stigma is so situated 
that the pollen does not directly fall upon it; but 
then these flowers have, as mentioned before, hair 
or other processes, which oblige the insects to 
enter them along the stigma; so that, when they 
return or visit the flower repeatedly, they must rub 
the pollen against the stigma. 
Such plants, as on one stem have both female 
and male flowers, are mostly impregnated by insects 
alone. Only those impregnate themselves, which 
have no nectaries, or when the male flowers stand 
close to the female flowers, as in some species of 
gramina; Typha; Coix; Carex, and others. In 
that case such flowers have their female flowers 
situated lower than the male flowers, and their pe- 
tals are very minutely or very deeply laciniated, so 
that the pollen when falling, can reach them. ‘This 
is the case, for instance, with the different species 
of Pinus and similar trees. Here probably the wind 
too is of some service. It disperses the pollen in 
the air, so as often to involve the tree in a kind of 
cloud. 
