CASUALTIES OF VEGETABLES. CHAP. XfL 



Now its surface is verdant and shining, and in an 

 itstant it changes to a yellow, and its brillancy is 

 gone. If the substance is cut into, the parts are 

 found to have lost all cohesion, and are quite rotten; 

 the only remedy is speedy amputation below the 

 diseased part. Sometimes the vital principle col- 

 lecting and exerting all its energies, makes a stand 

 as it were against the encroaching disease, and 

 throws off the infected part.* 



SUBSECTION VIII. 



Occasion- Etiolation. Plants are sometimes affected by a 

 f light?" 1 disease which entirely destroys their verdure, and 

 renders them pale and sickly. This is called etiola- 

 tion) and may arise merely from want of the agency 

 of light, by which the extrication of oxygene is ef 

 Rationale, fected, and the leaf rendered green. And hence it is 

 that plants placed in dark rooms, or between great 

 masses of stone, or in the clefts of rocks, or under 

 the shade of other trees, look always peculiarly 

 pale. But if they are removed from such situations 

 and exposed to the action of light, they will again 

 recover their green colour. 



Etiolation may also ensue from the depredation 

 of insects, nestling in the radicle, and consuming 

 the food of the plant, and thus debilitating the 

 vessels of the leaf so as to render them insuscepti- 

 ble to the action of light. This is said to be often 

 * Smith's Introxluction, p. 340. 



