THE DEBT OF BLOSSOM TO INSECT 57 
and ourselves with food and keep the air duly supplied 
with oxygen for the purposes of respiration ; but now 
we begin to see the other side of the account, we realize 
in this, the sixth Factor of Life, that the debt is not 
all on one side, but that, in their turn, the bright 
blossoms which add so much to the pleasure and 
beauty of life depend for their continuance from 
generation to generation upon the insects. In the 
caterpillar stage they eat the leaves, or other parts of 
this plant or that, but they make up for it by 
pollinating the stigmas now that the crawling grub 
has changed into a beautiful moth or butterfly, or 
perhaps into a beetle, a fly, or some other insect. 
I do not mean that if there were no insects there 
would be no plants ; but I do mean that in all proba- 
bility there would be no bright blossoms and no sweet 
perfumes, but only such wind-pollinated flowers as 
those of the Grasses, the Hazel, the Sedges, and the 
Pine. 
Thus, while the animals depend upon the plants 
for breath and food, they render good service in return 
in the important matter of reproduction, as well as 
in other ways which will come before our notice in 
the sequel. 
We must pass over all those complex happenings 
between the pollination of the stigma and the ripening 
of the seeds of which we can see but little and make 
out nothing without a great deal of hard work and 
training. What we can observe with the naked eye, 
however, is full of interest. We can watch the small 
pistil of the Wallflower grow into the long pod, full 
of seeds, and see it split open to allow of their being 
blown away, or the pistil of the Bramble turn into the 
Blackberry ; we can witness the development of Peas 
