PLANTS THAT ARE ATHLETES 79 
to be scattered abroad, the stem holding the pod 
becomes erect, the pod itself raises its head until it 
is level with or above the leaves, when it divides it- 
self into three valves, laying them back horizontally 
so that the seeds may not fall out; and then begins 
the process of shooting. As the hard, dry 
edge of the valve contracts it presses the under 
side of the outer row of seeds; they, in turn, 
pressing on the middle rows. As fast as 
one seed is projected another rolls down and 
takes its place, the hard edges of the valve often 
curling together to force out the last remaining one. 
By this mechanical expulsion of its seeds the violet 
is enabled to secure a wide distribution of its species. 
It need have no fear of its seeds falling so close 
about the parent plant that all will be crowded, and 
so die for lack of air and sunshine and nourishment 
from the earth. 
There are numerous other kinds of gunners and 
archers among the plants, and, just as with man, 
their guns or projectors and their manner of shoot- 
ing are widely different. The common yellow 
oxalis or “sheep sorrel” has developed the shoot- 
ing-habit to a wonderful degree. Its tiny seeds are 
covered with thin, skin-like bands that act, when 
touched, like elastics on a sling-shot, by suddenly 
curling up with sufficient force to shoot the tiny 
