96 



THE STEM. 



ilar bud at the close of the season, which in its development re- 

 peats the same process. 



145. These yearly growths, in trees with well-formed Scaly 



Buds, such as the Magnolia 

 (Fig. 130), the Horsechestnut 

 (Fig. 127), &c., are plainly 

 marked by the assemblage of 

 scars or rings on the bark (<z), 

 which mark the places where 

 the bud-scales were attached. 

 The reason why these, and 

 the leaf-scars, are obliterated 

 after a few years will appear 

 when the increase of the stem 

 in diameter is considered. 

 The "bud-scales themselves, 

 which so closely overlie each 

 other and protect the tender 

 parts within against injury 

 from moisture and sudden 

 changes of temperature dur- 

 ing the dormant state,* are 

 only a special modification 

 of leaves, developed in this 

 shape at a time when the internodes have ceased to elongate ; 

 so that the space between each ring in the figure just referred to 

 represents an undeveloped internode. Such a stem displays alter- 

 nately two modes of growth. First, the internodes elongate and 

 interspace a succession of leaves, making the proper vegetation of 



* The more effectually to ward off moisture, they are commonly covered 

 with a waxy, resinous, or balsamic exudation (as in the Poplar especially), 

 impervious to rain, but which is melted by the heat of the sun when it stimu- 

 lates the bud into growth. To guard against sudden changes of temperature, 

 they are often lined, or the rudimentary leaves within are invested, with non- 

 conducting down or wool. 



FIG. 126. Diagram of a longitudinal section of a bud, such as that of the Horsechestnut. 



FIG. 127. A year's growth of a Horsechestnut branch, crowned with a terminal bud : a, 

 scars left by the bud-scales of the previous year : b, scars left by the fallen leaf-stalks : c, axil- 

 lary buds. 



FIG. 123. Diagram to illustrate the development of the bud in Fig. 126, 127. 



FIG. 129. Branch and buds (all axillary) of the Lilac. 



