256 



A TEXT-BOOK OF BOTANY 



sling-fruits. In the violet and the witch-hazel, when the 

 seed-vessel splits, its walls press upon the seeds so that they 

 are pinched out, as a moist apple-seed is projected by being 

 pressed between the thumb and the finger (Fig. 248). 

 When the pod of the wild bean bursts, the two valves twist 



violently and throw 

 the seeds (Fig. 249). 

 In the touch-me- 

 not, or the balsam, 

 a strain is devel- 

 oped in the grow- 

 ing wall of the 

 seed-vessel, so that 

 at rupture, which 

 may be brought 



FIG. 250. Winged fruit of maple. After KEENER. about by slight 



pressure, the pieces 



suddenly curl up and throw the seeds. The squirting 

 cucumber is so named because it becomes very much 

 distended with water, which is finally forcibly ejected 



FIG. 251. Winged seed of Bignonia. After STRASBURGER. 



along with the mass of seed. In tropical forests there 

 are plants whose large seed-vessels explode with a loud 

 report. 



