306 
DARWINISM 
CHAP. 
by floating in rivers and lakes, and thus reaching other locali¬ 
ties. During the elevation of land areas this method would 
be very effective, as the new land would always be at a lower 
level than that already covered with vegetation, and therefore 
in the best position for being stocked with plants from it. 
The other modes of dispersal of seeds are so clearly adapted 
to their special wants, that we feel sure they must have been 
acquired by the process of variation and natural selection. 
The hooked and sticky seeds are always those of such her¬ 
baceous plants as are likely, from their size, to come in 
contact with the wool of sheep or the hair of cattle • while 
seeds of this kind never occur on forest trees, on aquatic 
plants, or even on very dwarf creepers or trailers. The 
winged seed-vessels or seeds, on the other hand, mostly belong 
to trees and to tall shrubs or climbers. We have, therefore, a 
very exact adaptation to conditions in these different modes of 
dispersal; while, when we come to consider individual cases, 
we find innumerable other adaptations, some of which the 
reader will find described in the little work by Sir John 
Lubbock already referred to. 
Edible or Attractive Fruits. 
It is, however, when we come to true fruits (in a popular 
sense) that we find varied colours evidently intended to 
attract animals, in order that the fruits may be eaten, while 
the seeds pass through the body undigested and are then in 
the fittest state for germination. This end has been gained in 
a great variety of ways, and with so many corresponding 
adaptations as to leave no doubt as to the value of the result. 
Fruits are pulpy or juicy, and usually sweet, and form the 
favourite food of innumerable birds and some mammals. They 
are always coloured so as to contrast with the foliage or 
surroundings, red being the most common as it is certainly the 
most conspicuous colour, but yellow, purple, black, or white 
being not uncommon. The edible portion of fruits is developed 
from different parts of the floral envelopes, or of the ovary, in 
the various orders and genera. Sometimes the calyx becomes 
enlarged and fleshy, as in the apple and pear tribe ; more 
often the integuments of the ovary itself are enlarged, as in 
the plum, peach, grape, etc.; the receptacle is enlarged and 
