304 DARWINISM 



Colours of Fruits. 



It is when we come to the essential parts of plants on 

 which their perpetuation and distribution depends, that we 

 find cokjur largely utilised for a distinct purpose in flowers 

 and fruits. In the former we find attractive colours and 

 guiding marks to secure cross - fertilisation by insects ; in 

 the latter attractive or protective coloration, the first to 

 attract birds or other animals when the fruits are intended to be 

 eaten, the second to enable them to escape being eaten when 

 it would be injurious to the species. The colour phenomena 

 of fruits being much the most simple will be considered first. 



The perpetuation and therefore the very existence of each 

 species of flowering plant depend upon its seeds being pre- 

 served from destruction and more or less eff'ectually dispersed 

 over a considerable area. The dispersal is eft'ected either 

 mechanically or by the agency of animals. Mechanical dis- 

 persal is chiefly by means of air-currents, and large numbers 

 of seeds are specially adapted to be so carried, either by being 

 clothed \Wth down or pappus, as in the well-known thistle and 

 dandelion seeds ; by having wings or other appendages, as in 

 the sycamore, birch, and many other trees ; by being thrown 

 to a considerable distance by the splitting of the seed-vessel, 

 and by many other curious devices.^ Very large numbers of 

 seeds, however, are so small and light that they can be carried 

 enormous distances by gales of wind, more especially as most 

 of this kind are flattened or curved, so as to expose a large 

 surface in proportion to their weight. Those which are 

 carried by animals have their surfaces, or that of the seed- 

 vessel, armed with minute hooks, or some prickly covering 

 which attaches itself to the hair of mammalia or the feathers 

 of birds, as in the burdock, cleavers, and many other species. 

 Others again are sticky, as in Plumbago europsea, mistletoe, 

 and many foreign plants. 



All the seeds or seed-vessels which are adapted to be 

 dispersed in any of these ways are of dull protective tints, so 

 that when they fall on the ground they are almost indis- 

 tinguishable ; besides which, they are usually small, hard, and 



^ For a popular sketch of tliese, see Sir J. Lubbock's Flowers, Fruits, and 

 Leaves^ or any general botanical work 



