CHAPTER XXII 



DISPERSAL OF SEEDS 



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

 as widely as possible. It has a better chajice 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 O.xalis. 



An exploding pod is shown 

 at c. The dehiscence is 

 shown at h. 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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