STEMS 



U 



canes, usually with one or two buds and nodes, are spurs. When 

 these are left for the purpose of bearing spurs the following year, 

 they are called renewal spurs. In most species of grapes, woody 

 tissue interrupts the pith at the nodes; this is the diaphragm 

 (Fig. 4). 



19. The growth of stems in length. — A Mid is an incipient 

 shoot. Growth in length of stem continues from the terminal 



Fig. 3. A grape vine and its parts : a. trunk ; b. arm ; c. head ; d. cane ; 



e. shoot; f. spur. 



bud ; a stem branches from lateral buds. Growth in length con- 

 sists in the emergence of new nodes and internodes from the 

 terminal bud. This emergence is due to the elongation of the 

 internodes. The amount of elongation varies in different parts 

 of the same plant and greatly in different plants. When a stem, 

 through its branches or branchlets, has made its season 's growth, 

 the internodes do not lengthen in subsequent seasons. Increased 

 length in shoots takes place only by the addition of new inter- 



