CHAPTER XXII 



DISPERSAL OF SEEDS 



IT is to the plant's advantage to have its seeds distributed 

 as widely as possible. // has a better chance of surviving 

 in the struggle for existence. It gets away from competi- 

 tion. Many seeds and fruits are of such character as to 

 increase their chances of wide dispersal. The commonest 

 means of dissemination may be classed under four heads : 

 explosive fruits ; transportation by wind ; transportation by 

 birds ; burs. 



FIG. 249. EXPLOSION OF 

 THE BALSAM POD. 



FIG. 250. EXPLOSIVE 

 FRUITS OF OXALIS. 



An exploding pod is shown 

 at c. The dehiscence is 

 shown at b. The structure 

 of the pod is seen at a. 



Explosive Fruits. Some pods open with explosive force 

 and discharge the seeds. Even bean and everlasting peas 

 do this. More marked examples are the locust, witch 

 hazel, garden balsam (Fig. 249), wild jewel-weed or impa- 

 tiens (touch-me-not), violet, crane's-bill or wild geranium, 

 bull nettle, morning glory, and the oxalis (Fig. 250). The 



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