242 NATURAL SCIENCE [October 1898 
increased brilliancy has been of advantage. But the bees for whose 
favours the plants were bidding would have ruined all, had not the 
plants on their side had a very marked characteristic: infertility 
with varieties of the same species, or with other species of the same 
genus. The bees have constancy enough to ensure frequent cross- 
fertilisation between plant and plant within one variety or species: 
but, intent upon their own business, they take no trouble to put 
barriers between new varieties. This work is done by the plants 
themselves. The varieties, at any rate all the large number that 
have survived, have kept themselves apart. Through this inter- 
sterility the bees have been gardeners who had each variety and 
each species in an isolated garden, and for whom each new variety 
as it arose proceeded to isolate itself without any trouble on their 
part. They with their colour-sense and the plants with their 
preference for pollen from one of their own species, or even for 
pollen from one of their own variety have, working together, given 
us all the colours, shapes, and scents of flowers. 
F. W. HEADLEY. 
HAILEYBURY COLLEGE. 
