54 



THE CANADIAN HORTICULTURIST. 



erside. Every living- and growing" part of 

 the tree therefore, is increased in thickness 

 each year by a layer of new wood, just inside 

 the outer bark. In any cross section of a 

 trunk or branch, these annual deposits may 

 be seen in the form of distinct concentric 

 rings. By counting these rings, we may tell 

 the age of the tree, or any part of it, and by 

 acomparison of the relative sizes of the rings, 

 we may also learn much of the history of the 

 tree, and the times . through which it has 

 passed. A thick ring naturally represents a 

 season of good growth, while a narrow one 

 near it indicates that growth in some way 

 has been checked. It may have been by lack 

 of cultivation, or draught or by the ravages 

 of caterpillars on the foliage. Each ring is 

 an annual chapter in the history of the tree, 

 and the more we study the nature and habits 

 of trees, the better are we able to read the his- 

 tory written in these rings. 



Experiments to Prove Theories. 



As a means of proving that the annual in- 

 crease comes from the downward flow of the 

 cambium, rather than from the direct up- 

 ward flow of the sap, as is often supposed to 

 be the case, we have only to tie a band 



Ol" fnches 



34: inches 



Fig. 2243. A young tree, in which the growth 

 is checked by label wire. 



Fig. 2244. A pine girdled by mice. The lower 

 part has only four annual rings while the upper 

 part has eight. (From Bailey's Pruning Book.) 



tightly about any rapid growing part, so as 

 to check the downward course of the cam- 

 bium, and note the rapid increase in growth 

 above the band just as a dam thrown across 

 a stream increases the volume of the stream 

 above it. 



The accompanying illustrations show this 

 very clearly. 



That the new growth is laid on each year 

 in rings just beneath the inner bark may be 

 proven by lifting a corner of bark and insert- 

 ing beneath it a thin sheet of tin foil, then 

 binding the bark in place again so that it 

 will rapidly heal over. Before long all trace 

 of the wound will have disappeared, but 

 when the trunk is cut through at that point, 

 the tin foil will be found to be covered with 

 a ring of wood corresponding to each year 

 that has elapsed since it was placed there. 



The annual laying on of new growth may 

 also be easily seen in the gradual healing and 

 covering over of wounds made in pruning. 



