FIRST LESSONS IN FRUIT GROWING. 



D5 



How Tree Trunks Lengthen. 



So much for the growth hi thickness. 

 Now let us see how growth in height and 

 length takes place. 



The same flow of sap to the leaves, and 

 return flow of cambium which causes the 

 increase in thickness of any of the parts of 

 the tree, causes the rapid development of 

 new cells of wood at the extremities of the 

 branches ; and the lengthening of a branch 

 or the increase in height of a tree takes place 

 only by the addition of new growth at its ex- 

 tremity, any part below the extremity in- 

 creases only in diameter. The trunk of a 

 tree, therefore, does not lengthen, except by 

 the pruning off of the lower branches of the 

 head. If this is the case, the question might 

 be asked : " How then do we account for 

 the great high trunks in forest trees, where 

 no pruning knife could ever have been 

 used ?" Such trunks are the result of 

 Nature's pruning. One by one, the lower 

 branches have all been smothered out and 

 killed by crowding trees, and as each branch 

 has rooted and fallen away, the resulting 

 wound has been covered over by new growth 

 till we have at last the high smooth trunk, 

 with no sign of the lower branches that once 

 grew from its sides even to the ground. But 

 the man in the saw-mill, who cuts this trunk 

 into lumber, has plenty of evidence of their 

 existence by the knots found in the lumber. 

 Near the base of the trunk, these knots are 

 all near the centre of the log, but the farther 

 the cut from the base, the nearer the knots 

 come . to the surface, till near the top the 

 uncovered wounds and dead stubs may easily 

 be seen. 



One of the practical lessons for the fruit- 

 grower to learn from this is that the trunks 

 of his fruit trees do not lengthen, and he 

 should therefore be careful in dealing with 



Fig. 2245. Scheme to illustrate the arrangement 

 of annual growth. 1,2,3 etc ; represent the parts 

 of the stem grown during the first, second, third 

 etc ; twenty years of the life of the tree. K. Knots; 

 the shaded part of each is the dead ki^ot of lumber. 

 (U. S. Bulletin, Forestry for Farmers. ) 



young trees to start the heads at the desired 

 height to begin with, and not have to prune 

 off large limbs afterward to the detriment of 



the tree. 



H. L. HuTT. 

 O. A. C. Guelph. 



