60 
SEED DISPERSAL. 
are made and how they behave. A considerable number 
of seed pods have been illustrated with notes in recent 
schoolbooks. Here are some of them : 
peas and vetches, and some kinds of 
beans, violets, balsams, wood sorrel, 
geranium, castor bean, some of the 
mustards and cresses and their cousins, 
Alfilerilla, richweed, Pilea, witch-hazel, 
and others. Each of those will well 
repay study, especially the fruit and 
seeds of oxalis. The witch-hazel bears 
a hard, woody, nut-like fruit, as large as 
a hazelnut; when ripe, the apex gaps 
open more and more, the sides pressing 
harder against each smooth seed, till 
finally it is shot, sometimes for v a dis- 
riG. 48 .-r> r y fruit; °f witeh- tance of thirty feet. The girl who has 
shot an apple seed or lemon seed with 
pressure of thumb and finger across a small room, can 
understand the force needed to shoot a seed but little 
heavier than that of the apple two or three times that 
distance. 
