220 COMPOUND ORGANS OF PLANTS. 



; 



CHAPTER XVII. 



ON THE DISPERSION AND GERMINATION OF SEEDS. 



IT must be obvious that the immense quantity of seed which 

 plants generally produce, could never germinate in their imme- 

 diate neighborhood, and therefore, as the seed ripens, the peri- 

 carp gradually assumes such an organization as is calculated to 

 effect its dispersion or removal to a more distant locality. The 

 dissemination of the seeds is the result of the peculiar organi- 

 zation of their pericarp or seed-vessels, rather than of the seeds 

 themselves, which in this respect present some of the most 

 interesting and beautiful contrivances in nature. 



Sometimes the pericarp opens elastically with a spring-like 

 mechanism, and discharges the seed contained in its cavity to 

 a considerable distance. The seeds of the castor oil plant, of 

 the common garden balsam, and of the common furz, or whin- 

 bush of Europe, are separated from their pericarps in this 

 manner. In Hura crepitans, a plant which grows in the West 

 Indies and in South America, the seeds are projected from 

 the strong bony envelope of the pericarp as soon as it opens, 

 which it does with immense force and with a report as loud as 

 a pistol. 



The pericarps of the thistle, dandelion, and other species of 

 Composite, have attached to them a beautiful stellate down; 

 contrivances which are evidently intended to catch the wind, 

 and by means of which they are removed when fully ripe from 

 off the surface of the receptacle of these plants, and wafted to 

 a distance to spots favorable to their germination. The peri- 

 carps to which these appendages are attached, will sometimes 



