THE WORK OF STEMS 



249 



of union and examine under the microscope. If possi- 

 ble, try some experiments in grafting. For directions 

 see Hunn and Bailey: "The Practical Garden 

 Book" ; also consult some one who is skilled in the 

 matter. 



The cambium is not the only 

 portion of the stem that grows, for, 

 as we have already learned, the 

 stem grows in length at the tip. We 

 may divide the tip into three re- 

 gions (Fig. 143) : (a) the extreme 

 end, occupied by a bud in which 

 leaves are continually being formed ; 

 we may call this the formative re- 

 gion; (b) the elongating region, just 

 back of the formative region (see 

 page 77), and (c) the maturing re- 

 gion (region of differentiation), in 

 which the various tissues, having 

 ceased almost entirely to grow in size, assume their 

 characteristic forms and structures. It will be noticed 

 that the buds are formed in the axils of leaves (i. e., 

 just above the junction of the leaf and stem) ; excep- 

 tions to this are the buds formed from callus (see 

 page 263) and the buds formed on roots, e. g., the 

 buds which grow up into sprouts or suckers from the 

 roots of fruit trees, Poplars, Elms, etc. 



A peculiar method of growth at the joints or nodes 



143. Terminal part of a 

 growing branch: (a) 

 formative region, (6) 

 elongating region, (c) 

 maturing region (region 

 of differentiation). 



