PLANTS DEFEND THEMSELVES 37 
forces. Horses, cattle, and sheep fear and avoid it; 
small animals dodge around it; even man refrains 
from too much intimacy. It has developed an ex- 
tremely sharp thorn at the end of each branch; at 
the base of the branch is a bunch of spine-like 
needles or thorns; and, in addition, each branch 
forms in itself a row of dagger-like points; the 
whole presenting a formidable resistance to the on- 
slaughts of destroying animals. And yet, even 
as with the strongest of humans, the hawthorn has 
its annoying, small enemies—numbers of them— 
such as caterpillars and fungi, which it cannot fight, 
but must tolerate. The hawthorn is, however, one 
of the most independent of plants; and being, like 
man, of sociable nature, as soon as its success in 
any locality is assured it begins to gather around it 
many agreeable neighbours. 
There are three types of dangers against which 
all plant life is forced to defend itself: insect pests; 
voracious animal and plant life; and destructive 
natural forces. 
For the land plants, the wingless insects, such 
as ants, are the chief enemies in the pest class. In 
plant life there is a rule that all insects which do 
not give value received must be repelled. 'The fly- 
ing insect, in acting as a carrier of pollen from 
plant to plant, earns the right to sip honey from 
