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 



