276 FERTILIZATION OF FLOWERS BY INSECTS. 
we blow upon one of its mature catkins, we see at once small 
clouds of pollen emitted and carried away, and if immediately 
after we examine the surrounding stigmas we find very few which 
have not some granules of pollen attached to them. In this exam- 
ple, as a condition of the easy dispersion of the pollen by means 
of the wind, we have the excellent form of inflorescence of the 
male flowers arranged in catkins freely suspended in the air, and, 
as a condition of an inevitable intercourse between individuals, we 
find a separation of the sexes, which is a quite general phenomenon 
in anemophilous flowers. In other cases, for example in the Plan- 
taginaceæ, the parts shaken by the wind are the anthers which 
hang suspended from long and very weak filaments, and the inter- 
course between individuals is obtained not by a separation of the 
sexes, but by a difference of time in the development of the sexual 
organs. In these plants, while the anthers are yet immature and 
enclosed within the floral envelope, the stigmas, perfectly mature, 
have already appeared in the form of long, plumose stalks; and 
only when the stigmas have passed maturity do the anthers ap- 
pear. Such are the principal characteristic differences of anemo- 
philous flowers. 
The flowers fecundated by the intervention of insects are far 
more highly differentiated in the disposition of their parts. Yet 
here, too, some general conditions necessary to secure the visits of 
insects, and the transfer of pollen by their means can easily be 
determined. And in the first place, it is necessary that the insects 
should be able to distinguish such flowers at a distance. Now this 
can only obtain in three ways, either by means of the colors, or 
the odors, or both colors and odors at the same time. And this @ 
priori deduction from the Darwinian doctrine is in harmony with 
„the facts ; for entomophilous flowers are either colored, or odorous, 
or colored and odorous at the same time. In like manner, odors 
and colors are œ priori perfectly useless to anemophilous flowers, 
or those fecundated by the wind, and are not, therefore, properties 
which can be fixed by natural selection. With this, too, the real- 
ity corresponds perfectly, for anemophilous flowers have neither 
colors nor odors. 
. ‘what we here merely suppose, takes Place in reality. ‘The Plantago media is a pict 
which has 
ulousness of the anthers is lessened, the pollen has lost its anpami and the pianti is 
normally visited by 2: s terrestris, as I ascertained in the mountains above men- 
tioned. 
