94 



THE STEM, 



155 



156 



and fourth internodes, &c. have begun to lengthen long before the 

 first has attained its full growth. The stem thus continued from 

 a terminal bud is, if it survive, again terminated with a similar bud 



at the close of the season, which in its 

 development repeats the same process. 

 A set of narrow rings on the bark 

 (Fig. 153, a) commonly mark the limit 

 of each year's growth. These are the 

 scars left by the fall of the scales of 

 the bud ; and these, in the Horsechest- 

 nut, and other trees with large scaly 

 buds, may be traced back on the stem 

 for a series of years, growing fainter 

 with age, until they are at length ob- 

 literated by the action of the weather 

 and the distention caused by the in- 

 crease of the stem in diameter. The 

 same is the case with the more con- 

 spicuous leaf-scars, or marks on the 

 bark left by the separation of the leaf- 

 stalk, which are for a long time con- 

 spicuous on the shoots of the Horse- 

 chestnut (Fig. 153, h) and the Mag- 

 nolia (Fig. 155). 



160. A bud, therefore, is nothing 

 more than the first stage in the de- 

 velopment of a stem, with the axis still 

 so short that tlie I'udimentary leaves 

 within successively cover each other, 

 while the whole is covered and pro- 

 tected by the scales without. Buds 

 vary greatly, however, in size, ap- 

 2:)earance, and degree of development. 

 Those of many shrubs and trees are 

 minute, and hidden by the bark until 

 their vernal growth commences, as in 



FIG. 155. Branch of Magnolia TJmbreUa, of the natural size, crowned with the terminal 

 bud ; and below exhibiting the large, rounded leaf-scars, as well as the rings or annular scars 

 left by the fall of the bud-scales of the previous season. 156. A detached scale from a similar 

 bud ; its thickened axis is the base of a leafstalk ; the membranous sides consist of the pair of 

 stipules. 



