180 



A TEXTBOOK OF BOTANY 



[Ch. IV, 10 



overshaded, die, and fall away, after which the old bases 

 become buried as knots l)y the ever-increasing layers of the 

 wood. Thus in time the cone of foliage comes to stand at 





^, mP 









• 4' ^ 



It ; 







..!ti^V\ 



Fig. IJ 



4' ' / /i I 1 ir showing the t\p]L il i nni il form. 

 (I r 1111 B 111 \ ) 



the summit of a branchless columnar trunk which yields 

 our most valuable timber. Such stems do not show the 

 hollow-column principle of construction, except incidentally 

 when the heart wood is removed by tlecay, for the mode of 

 growth is such as to build a stout solid column. 



