DISPERSAL OF SEED BY PLANT 



409 



extents as they dry out, so that considerable tensions are 

 set up between them. At the same time the cells of the 

 separation tissue are weakening. There comes a point 

 when the tensions overcome the resistance of the separation 

 layer, which gives way suddenly. In the whin the valves 



mo. 



Fig. 64. — Campanula capsules : i, C.latifolia, pendent capsules with 

 basal pores ; 2, C. pyrenaica, erect capsules with apical pores. Nat. 

 size. 



bend in, in the broom they flick into a spiral. In both cases 

 the movement is violent and results in the seeds being 

 thrown to a distance of some feet. The minute explosions 

 of the pods of whin and broom, on a hot still day in late 

 summer, is an intimate and characteristic country sound. 



