TREKS AND FORESTRY 



11 



FIG. 3. STRUCTURE OF A TREE TRUNK 

 ONE YEAR OLD 



It is a series of cylinders one within 

 another. The cambium is the living 

 part 



-'Scion'-- 



-Cambium 



-Stock- 



M 





FIG. 4. KEY TO SUCCESS IN GRAFTING 



The living cambium of the ">cion" 

 must join exactly and become contin- 

 uous with the living cambium of the 

 "stock." or the process will not be 

 successful 



STRUCTURE AND LIFE OF A 

 TREE 



A TREE is an individual and as 

 such it is alive, with parts 

 dividing the labor pertaining 

 to life and cooperating for the good of 

 the whole; but, on the other hand, a 

 tree has only a .small fraction of it> 

 great mass made up of living sub- 

 stance. When very young, it consists 

 entirely of living substance; but long- 

 before one year has passed it contains a 

 large accumulation of dead material 

 the great bulk of which is "wood." 

 filling up and making strong the trunk, 

 branches and roots. 



The one-year old trunk, examined 

 from the central axis to the outside, has 

 a definite structure as follows: (1) a rod 

 of pith, (2 1 a cylinder of wood embracing 

 the pith, (3) a cylinder of inner bark 

 (bast), thinner-walled than the wood 

 cylinder and embracing it, and outside 

 of these, (4) an enfolding cylinder of 

 bark (Fig. 3). All send off parts to 

 right and left into the leaves and, after 

 the first year, into the branches. The 

 living part, called the cambium, a living 

 cylinder of scarcely appreciable thick- 

 ness, lies between the wood and the 

 inner bark. It i> easy to understand 

 why, in grafting, the living layer of 

 the branch to be attached must be made 

 to join exactly and become continuous 

 with the living layer of the branch which 

 is to receive it, or the grafting will not 

 be successful (Fig. 4). 



Each year this living cvlinder of 



