ON VEGETABLE PHYSIOLOGY. ?75 



ARTICLE III. 



ON VEGETABLE PHYSIOLOGY. 

 By J. Todd, Denton Gardens, Lincolnshire. 



1. The Hoots of Plants. 

 Vegetable physiology is that department of natural science which 

 treats of the structure and constitution of plants. It considers every 

 species of vegetable as an aggregation of nicely adjusted organs, each 

 of which is designed for a particular function ; and the changes pro- 

 duced by their mutual action, constitute what we call the vital prin- 

 ciple, or life of the plant. Thus, for example, the root, stem, and 

 leaves, are the chief organs of nutrition, and the flowers those of fruc- 

 tification ; and so long as they remain subservient in the performance 

 of their appropriate functions,[the individual will continue to live, and 

 possess the power of propagating its kind. Now as all plants that 

 flourish beneath the gardener's fostering hand, are but so many 

 beautiful combinations of these exquisitely-constructed parts, it follows 

 that some acquaintance with vegetable physiology will prove of the 

 greatest utility to every one concerned in the culture of a garden ; as 

 it furnishes correct knowledge of the structure of these several parts, 

 and of their adaptation to certain definite purposes, as well as of their 

 relative influence over each other, and of the influence of various 

 modifying causes over the whole system. 



Having made these prefatory remarks on this beautiful and in- 

 teresting science, it now remains to detail its leading principles, and 

 the method of reducing them to practice, and rendering them subser- 

 vient in the ordinary management of a garden. 



As the roots of plants are the chief medium through which they 

 receive nourishment, some account of their structure, and of the 

 curious and simple mode by which they effect their object, will occupy 

 the remainder of this paper. The root may be defined to be, that 

 portion of a plant which grows in an opposite direction to the stem ; 

 and differing from the latter in its remarkable downward tendency, 

 and from its disposition to shun the light of day. So powerful, indeed, 

 is this tendency to descend, " that no known force is sufficient to 

 overcome it." The chief object of the root appears to be that of fixing 

 the plant firmly in the earth, and of taking up a supply of moisture 

 from the humid medium by which it is surrounded. It usually con- 



