180 



A TEXTBOOK OF BOTANY [Ch. IV, 10 



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

 become buried as knots by the ever-increasing layers of the 

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



Fig. 122. — Abies vc.nusta, a Fir, showing the typical conical form. 

 (From Bailey.) 



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 decay, for the mode of 

 growth is such as, to build a stout solid column. 



