VEGETABLE PHYSIOLOGY. 99 



THE EMBRYO, OR INFANT PLANT That part of tht seed which 



is formed of the primary radicle, expanding ultimately into a 

 regular root; and of the plumula which ascends and becomes 

 the stem or trunk, and gradually the complete plant or tree. 



NUTRITIVE ORGANS The root and leaves. 



NUTRITIVE PROCESS. The capillary extremities of the radiculse, 



or smaller fibres of the root, enter the earth in different directions, 

 and absorb therefrom nutrient materials held in solution by 

 \rater ; and convey the fluid to the caudex, and thence into the 

 cells of the alburnum or sap wood, from which it is forwarded 

 by tubular vessels, through the stem and branches, to the leaves ; 

 where, by exudation, it parts with its superfluous water and 

 gases, and by absorption, takes np new ingredients from the 

 atmosphere, and forms the true sap. The sap, thus perfected, 

 is then conveyed back from the leaves by another set of tubular 

 vessels (termed cortical) into the cells of the bark ; and from 

 thence, supplies of nourishment are forwarded to every part of 

 the plant, including the branches, stem and roots. 



RE-PRODUCTIVE ORGAN. The flower, terminating in the fruit and 



seed. 



RE-PRODUCTIVE PROCESS. The anthera. situated at the summit of 



the stamen, and consisting of small globules, haying reached their 

 fullest degree of expansion, burst, and dropping their farina upon 

 the stigma of the pistil, they fertilize the ovary, which then 

 enlarges, until a new flower, and afterward the fruit are formed, in 

 which is imbedded the seed, containing the rudiments of a new 

 plant. 



GERMINATING AND VEGETATIVE PROCESS. The seed being 



deposited in the earth, by the chemical agency of heat and water 

 expands, until its outer coat bursts ; when the primary radicle 

 (already explained) first dips into the earth, and forms a root. 

 The plumula then ascends, and becomes the stem, and carries 

 with it the cotyledons, which now, by chemical agency, being 

 endued with nutritive properties, expand and are converted into 

 leaves, from which they supply the young plant, until the 

 common leaves have been formed, and until the radicle below 

 has sent out branches sufficient to absorb nourishment from the 

 ground. The cotyledons then, no longer being required, die 

 away, and the plant advances until it is completely formed into 

 item, branches, and leaves. 



