THE STRUCTURE OF STEMS. 



217 



passing from A at the right ; and the bark, with its 

 different layers, at the left. Trace these different 

 portions in the vertical section. 



EXEKCISE LXYIII. 

 The First Year's Growth. (CONTINUED.) 



The number and compactness of the woody bun- 

 dles in a young stem will depend upon the time of 

 the observation ; if it is made early in the season, 

 there will be few (Fig. 388), and their number will 

 increase with the growth and multiplication of the 



FIG. 888. 



FIG. 389. 



FIG. 390. 



leaves. This increase is shown in Fig. 389, where 

 six new bundles are seen inserted between the first 

 six shown in Fig. 388 ; while in Fig. 390, which rep- 

 resents a woody stem at the close of the year, they 

 are shown filling all the space, except the narrow 

 strips of the medullary rays. 



Bearing in mind the composition of a woody 

 bundle, as shown in the last exercise, look again at 

 the section of a dicotyledonous stem during the first 



