146 BOTANY. [CHAP. iv. 



is necessary to understand that the changes induced by 

 cultivation, popularly considered to raise the plant above 

 its previous level of development, are in reality always of 

 a degenerate nature, causing the plant to fall back to a 

 lower level, or by developing to an extraordinary extent 

 one part of its structure at the expense of the remaining 

 portions, and so disturbing the natural balance of its eco- 

 nomy, that when neglected it never retains the abnormal 

 condition assumed under cultivation, but soon returns to 

 the wild or normal state. There are two principal objects 

 in view in cultivating plants ; utility, as sources of food, 

 etc., and in the second place, as affording pleasure by the 

 very varied combinations of form, and colour, and per- 

 fume afforded. From the first standpoint, it will be 

 seen that, as a rule, as already stated, one particular 

 part of the plant is alone of value, hence those methods 

 of cultivation are adopted that favour the development 

 of this particular part. As illustrations may be named 

 the disproportionate quantity of fruit desired, and this 

 too, to be of the first class, must be free from seeds ; in 

 the potato plant, the swollen tips of certain underground 

 branches potatoes are alone of value, hence the 

 whole object of the gardener is to get an abnormally 

 excessive development of this portion of the plant. 

 When gardeners and their employers are educated up to 

 the point of realizing that the constitution of a plant, as 

 that of an animal, can be overtaxed, and that this over- 

 taxation results in disease, as manifested by the potato- 

 disease, and in fact the diseases of most of our important 

 food-producing plants, which can in many instances be 

 proved to result from abnormal treatment, and a craving 

 to obtain more from the plant than it can yield without 



