ELEMENTARY FORESTRY. 



rare cases we have two periods of growth in one year, as in 

 !s:m., when th- drouth o? midsummer ripened up the wood of 

 the frees'by the' first t>f' August and the rains of autumn started 

 a new growth, and caused some trees and shrubs to flower in 

 October, but such occurrences are very uncommon and the extra 

 rings formed are readily detected by their being smaller than 

 adjoining rings and less distinctly denned. The age of trees 

 could be told by the rings of the outer bark nearly as well as 

 by those of the wood were it not for the fact that the outer 

 layers of bark fall off as the tree grows older. 



In some experiments the bark of rapidly growing branches 

 was peeled back in the spring for a few inches, the wood 

 covered with tin-foil and the bark replaced. At the end of the 

 season there was found a ring of wood outside of the tin-foil, 

 thus shovving where the annual growth of the tree was made. 



The Bark covers the whole exterior surface of the trunk, 

 branches and roots and serves as a protection. It is made 

 up of two parts, the outer or corky layer which is dead bark 

 and the inner or live bark. These vary much in appearance 

 and thickness on different kinds of trees. For instance, on 

 the White Birch the corky layer is pure white, very thin and 

 tough while on our White Pine it is very dark brown and 

 often an inch or more in thickness and quite brittle. 



The Sapwood is the portion of the wood next to the bark. 

 It varies much in thickness in different species and in trees of 

 the same species: the most rapidly grown trees contain the 

 largest amount. It is the most active portion of the wood in 

 the growing tree, and contains considerable plant food and 

 more water than the heartwood. 



The Heartwood is the wood in the center of the trunk and is 

 generally distinguished from the sapwood by its more compact 

 structure and darker color, though in some cases it may be 

 lighter colored than the sapwood. It is also harder and more 

 valuable for fuel, shrinks less in drying, and is more durable 

 in contact with the soil than the sapwood. There is very 

 little movement of the sap in the heartwood, and it contains 

 less water than sapwood. 



The Roots furnish water and nourishment that the plant re- 

 ceives from the soil but only the young roots have the power 



