264 



not be iuappropriate in this place, and prove interesting to 

 botli. 



From what has been observed of this evil, it appears, that 

 it exists in a remarkable manner, only among exposed 

 plants, and that heat resulting from shelter, in most cases, 

 furnishes a complete preventive. In consideringt he nature 

 and habits of woody plants, we find, that the warmer the 

 atmosphere in which they grow, the more active the vege- 

 tation that is carried on in them, and consequently the 

 greater the deposition of nutrient matter, that is made in 

 the bodies of the plants. Our object, therefore, should be, 

 after their removal to colder or more exposed situations, so to 

 increase by artificial methods the action of their vegetable 

 powers, as to compensate to the required extent for the 

 absence of heat ; and should that not be done sufficiently in 

 the beginning, to augment it afterwards. This important 

 principle was stated above, in the instrucdons given for the 

 preparation of the soil, but not sufficiently illustrated under 

 that head.* 



It is on this principle, that the application of the rich and 

 friable compound above mentioned is made with such extra- 

 ordinary effect. If we administer it to two park trees of the 

 same species, and of equal size and strength, but placed in 

 different degrees of exposure, in equal quantities, the shoots 

 which the trees send forth, will not be in the ratio of the 

 compound applied, but in the ratio of the exposure. In the 

 same way, if we apply the one half of the compound to a 

 park tree comparatively sheltered, and double the quantity, 

 or more, to a similar tree severely exposed, the shoots which 

 are sent forth by the former, will be fully equal to those sent 

 forth by the latter. Thus, the uniform, but relative success 

 attending this practice demonstrates the justness of the 

 principle. 



* See Sect. VI. p. 193—195. 



