112 THE HUMAN SIDE OF PLANTS 
aerial navigation as a sort of chance or happening 
of no special importance; but it is vitally important, 
not only for the success of the plant, but for man- 
kind as well. 
Some plants send their seed-children out by 
means of spines and hooks, others shoot them out to 
places of safety, still others float upon the water, 
as the cocoanut; again some roll and tumble to a 
suitable home. All of these methods of dispersal 
are used; to say nothing of the work of birds and 
animals in aiding them to distribute the seeds in 
places where competition is not too strong, and 
where climatic conditions will be conducive to their 
best growth; but there is a large group of plants 
that have adopted by far the most ingenious method 
of sending their children into the world—that is, by 
means of airships. Plants of this kind may be 
grouped into several classes according to their 
method of navigating the air. 
The seed-children of the elm-tree and those 
of the maple and the ash have wings—like Icarus of 
old—and fly somewhat like birds; those of the hop- 
tree are surrounded by a peculiar kite-like structure 
with the seed in the centre of this thin membrane; 
the sycamore keeps its children snugly rolled to- 
gether in a ball until they are fully developed, when 
each one flies forth by means of a winged-arm 
