156 



THE FRUIT 



several valves, already in a high state of tension, the 



touch which 

 produces the 

 explosion 

 merely in- 

 creasing the 

 stress along the lines 

 of dehiscence. The 

 opened valves of the Vio- 

 let fruit, constricting, 

 cause the forcible expul- 

 sion of the seeds one after 

 another. The hard, bony 

 capsules of the Witch- 



281. Fruit of Witch-hazel discharging hazel (Fig. 281), contract- 

 ing, squeeze the smooth, 



hard seeds with much force ; and the seeds are shot to a 

 distance of many feet. 1 



Supplementary Reading 



1. Plants that bury their Seeds. Lubbock's " Flowers, Fruits, and 

 Leaves," pp. 85-88. 



2. The Fruits and Seeds of Plants Parasitic on Trees. Same 

 source, pp. 83, 84. 



3. Dispersal of various Fruits and Seeds. Same source, Chap. III. 



4. Dissemination of Plants by Ocean Currents and by Migrating 

 Birds. Darwin's " Origin of Species," Chap. XI, Dispersal. 



1 If a bough with the ripe but unopened fruits is hung on the wall of 

 one's room, the force with which the seeds are ejected and the distance 

 to which they fly are likely to be observed. 



Distances to which seeds are ejected by several plants are given by 

 Kerner and Oliver ("Natural History of Plants," II, 839) as follows: 



Cardamine impatiens 3 ft. 



Viola canina 3 ft. 



Geranium palustre 8 ft. 



Lupinus digitatus ." 23 ft. 



Acanthus mollis 31 ft. 



Hura crepitans 48 ft. 



Bauhinia purpurea 51 ft. 



