170 



THE STEM PROPER 



317. — Section of branch 

 showing knot. 



■ 





circumference of the stem ; how many years has the tree 



lived since the knot was formed ? Does this agree with 

 the age of the knot as deduced from 

 its own rings ? (As the tree may con- 

 tinue to live and grow indefinitely after 

 the bough which formed the knot died 

 or was cut away, there will probably 

 be no correspondence between the two 

 sets of rings, especially in the case of 

 old knots that have been covered up 

 and embedded 

 in the wood.) 



The longer a dead branch remains 



on a tree the more rings of growth 



will form around it before covering 



it up, and the greater will be the 



disturbance caused by it. Hence, 



timber trees should be pruned while 



very young, and the parts removed 



should be cut as close as possible to 



the main branch or trunk. Some- 

 times knots injure lumber very 



much by falling out and leaving the 



holes that are so often seen in pine 



boards. In other cases, however, 



when the knots are very small, the 



irregular markings caused by them 



add greatly to the beauty of the wood. The peculiar 



marking of bird's-eye maple is caused by abortive buds 



buried in the wood. 



11 





y.^\ 



318 319 



318, 319. — Diagrams of tree 

 trunks, showing knots of dif- 

 ferent ages : 318, from tree 

 grown in the open; 319, from 

 tree grown in a dense forest. 



PRACTICAL QUESTIONS 



1. Name the principal timber trees of your neighborhood. What 

 gives to each its special value? 



2. Which is better for timber, a tree grown in the open, or one in 

 a forest, and why? (239.) 



3. What are the objects to be attained in pruning timber trees? 

 Orchard and ornamental trees? 



