58 PLANT MIGRATION 
out through the open side. In the Cranesbills the jerk 
is so violent that seeds may be flung to a distance of 
twenty feet. One of the most efficient of all devices 
of this kind is found in the Sand-box Tree (Hura 
crepitans), a native of South America. By sudden 
rupture and twisting of the carpels of the woody sub- 
globular fruit, the large seeds of this plant are thrown 
Fic, 9.—FRUIT OF GERANIUM. 
a, Mature; b, ditto, with pouches raised ready to discharge 
nuts ; ¢, in act of discharging. 
to a distance of thirty yards, the explosion being 
accompanied by a report like that of a pistol-shot. In 
the common Dog Violet (Viola Riviniana) (Fig. 10) 
the fruit is a three-valved capsule, which on ripening 
divides; each valve assumes a horizontal position and 
its edges contract till it is shaped like an open boat, 
the seeds lying in a row down the middle. The sides 
as they dry close in tighter and tighter on the seeds, 
