166 NODES INTERNODES. [BOOK i. 



mentioned occurs in all plants, it follows that all plants must 

 necessarily have, at an early period of their existence at least, 

 both stem and root ; and that, consequently, when plants are 

 said to be rootless, or stemless, such expressions are not to 

 be considered physiologically correct. 



The STEM has received many names ; such as caudex 

 ascendens, caudex intermedius, culmus, stipes, truncus, and 

 truncus ascendens. It consists of bundles of vascular and 

 woody tissue, embedded in cellular substance in various ways, 

 and the whole enclosed within an epidermis. The manner 

 in which these parts are arranged with respect to each other, 

 will be explained hereafter. The more immediate subject of 

 consideration must be those organs which are common to all 

 stems. 



1. Of its Parts. 



Where the stem and root, or the ascending and descending 

 axes diverge, there commences in many plants a difference of 

 anatomical structure, and in all a very essential physiological 

 dissimilarity; as will be hereafter seen. This portion of the 

 axis is called the neck or collum, (coarcture of Grew, nceud 

 vital of Lamarck, limes communis, or fundus plantae, of 

 Jungius,) and has been erroneously thought by some to be 

 the seat of vegetable vitality. At first it is a space that we 

 have no difficulty in distinguishing, so long as the embryo, 

 or young plant, has not undergone any considerable change ; 

 but in process of time it is externally obliterated ; so that in 

 trees of a few years' growth its existence becomes a matter of 

 theory, instead of being actually evident to our senses. 



Immediately consequent upon the growth of a plant is the 

 formation of leaves. The point of the stem from whence these 

 arise is called the node (geniculum, Jungius), and the space 

 between two nodes is called an internode (merithallus, Du Petit 

 Thouars.) In internodes the arrangement of .the vascular 

 and woody tissue, of whatever nature it may be, of which 

 they are composed, is nearly parallel, or, at least, experiences 

 no horizontal interruption. At the nodes on the contrary, 

 vessels are sent off horizontally into the leaf; the general 

 development of the axis is momentarily arrested while this 



