DISPERSAL OF SEEDS, 152 
spring or rod with the seed sac attached remains fixed to the apex 
of the central column. When the seed is ripe the sac, instead of 
remaining close to the column, places itself at right angles to the 
column, it splits down the inner side, the edges separate, but there 
is a fringe of hair to keep the seed in place. When the right time 
arrives the springs jerk the sac up and outwards, throwing the seed 
out past the retaining hairs, the top of the spring and the sac 
remaining attached. 
GERANIUM PRATENSE (Meadow Crane’s-bill) has much the same 
arrangement for dispersing the seeds as the last two species. In 
this case the fruits ‘spring off in much the same way as in G. 
DissectuM, throwing the seeds out of the containing sac, but the 
‘springs are also detached from the apex of the central column. 
Thus it partakes of the methods of both species. All other species 
of the genus Geranium have an arrangement something of the same 
kind. 
The genus Eropium (Stork’s-bill) has the beaks or springs 
attached to the seed sacs spirally twisted when ripe. They often 
spring to a considerable distance from the parent plant. They are 
furnished on the inner side with long elastic bristles; being hygro- 
‘scopic, they uncurl when they become damp. This action gives the 
seed the power of locomotion at every change of atmospheric 
moisture. This action often causes the seeds to bury themselves, if 
they happen to fall on soft earth or sand. As all three species of 
the genus are found growing on sand, the seeds have every chance to 
bury themselves after they are discharged from the parent plant. 
The pods of the Pea and Bean tribe (the Lzauminos2) have, in 
some cases an arrangement for throwing the seeds to a distance. 
Take, for instance, a common Vetch (Vicia sEpIuM). When this pod 
is ripe it opens suddenly with a jerk, the two valves roll themselves 
up like corkscrews, one valve twisting to the right, the other to the 
left, throwing the round seed to some distance. This is caused by a 
