BOTANY. 123 



vegetation from the equator to the poles: this variety depends 

 upon the altitude at which they are found; the low land pro- 

 duces the most luscious fruits and stately trees, with a vast 

 variety of flowers and spices. 



As vegetation ascends the mountain heights, even under 

 the equator, it assimilates, according as the climate becomes 

 less congenial, to that of the colder regions, in the same way 

 as when receding from the equator towards the poles. Plants, 

 like animals, are liable to various diseases : no inorganic body 

 can be said to suffer from disease, although they are subject 

 to decomposition and disintegration, they are not capable of 

 diseased action, because destitute of vitality, which i^ indispen- 

 sable to such a process. Plants may become diseased from 

 a deficiency or excess of food, air, light, water, heat, or from 

 cold, noxious vapors, external injuries, insects, parasites and 

 hereditary organic or functional debility. They are also 

 liable to diseases peculiar to old age and excessive action, in 

 the same manner as animals. Thus they suffer from anemia,* 

 or want of fluids, like aged persons: they sometimes labor 

 under dropsy, from deficiency of light, and from other causes 

 they suffer and die from dry mortification* 



Lastly, plants are liable to disease and death from poisoning 

 and contagion. The economical uses of plants are well known, 

 and require only a passing notice : forest trees, and some parts 

 of other plants, are indispensable in the arts: cereals, fruits 

 and roots, are used as food for both man and beast : the grasses, 

 lichens, mosses and herbs serve as food for animals: various 

 plants, and the substances derived from them, are also used as 

 medicines. Plants designed for medicinal purposes should be 

 collected at a time when the whole vitality and forces are not 

 engaged in the growth of the plant and maturity of the flower 

 and seed : herbs should be gathered soon after flowering, or 

 when the seed is nearly ripened : roots, if annual, should be 



* Terms proposed by the author. 



