VEGETABLE 



ceptible, since the small swelling at tlie base of the single leaf which is there developed, 

 bears but little proportion to the size of the trunk of the 

 tree. 



The essential difference in structure between a node 

 and an internode is, that the bundles of wood are com- 

 pressed and turned aside in the former, so as to enter the 

 leaf, and thus a slight interruption to the course of the 

 general circulation ensues ; whilst, in the internode, the 

 bundles of woody fibre pass perpendicularly, and lie parallel 

 to each other. In some instances, as in the grasses with 

 hollow stems above mentioned, this compression or con- 

 traction of parts is so great, that a septum is formed across 

 the stem, dividing it into 

 two or more cavities. This 

 may readily be seen on 

 malting a perpendicular sec- 

 tion of a stalk of wheat, or 

 of the bamboo, and with the 

 septum of the latter may 

 sometimes be found the 

 flinty deposit before men- 

 tioned, under the term of 

 tabasshcer. They are then 

 said to be closed, in opposi- 

 tion to the pervious or open 

 condition, found when the 

 pith passes through it. 

 When the node surrounds 

 the stem, as in the grasses 

 and the hemlock, it is desig- 

 nated as entire; and when otherwise, as in trees, it 18 

 termed divided. 



As the essential element of a node is a new disposition 

 of the woody and other tissues, to meet the require- 

 ments of a leaf, it is manifest that wherever a node 

 exists there must be, or have been, a leaf, perfectly 

 or incompletely developed. In many instances the grow- 

 ing process ends after the formation of a node and before 

 the entire development of a leaf; and then will be formed 

 a leaf-bud, immediately above the base of a leaf. "When 

 such leaf-bud is evident, the node is termed compound ; 

 and when otherwise it is called simple. 



So far this account may suffice for both herbaceous and woody stems, but it is need- 

 ful here to interrupt our description, and consider herbaceous and woody stems sepa- 

 rately. This results from the great difference which is observed in the structure, as 

 well as in the degree of delicacy of organization of the two kinds of stems. 



Steins of Herbaceous Plants. Herbaceous plants are, for the most part, 

 annuals that is, such as are produced and die in the same season. It is, therefore, not 



a a the nodes, will 

 woody fibre passm;. 1 : from their 

 parallel course in the stem to 

 enter the leaf bud or the foot 

 stalk of a leaf. 



Figr. 104. A stem of the family 

 of grasses, showing at o 

 theenlargeme ts indicating 

 the existence of nodes. 

 The interval between the 

 two nodes is termed an inter- 

 node. 



