Current Literature. 257 



estimated to be five billion board feet which, not counting the in- 

 crement, should last thirty years at the present rate of cutting. 



The principal objections to the use of balsam for pulp are: (i) 

 In the ground-wood process the pitch covers the felts and cylinder 

 faces. The writer contends that this is not due to any property 

 of the wood itself, and must either come from bark left on the 

 surface of the blocks or else is formed in the process of grinding. 

 The statement is made that balsam fir is one of the fezv conifers 

 that lack resin ducts entirely, when as a matter of fact only four 

 out of thirteen indigenous genera contain ducts normally. (2) 

 The fiber of balsam fir is weaker, shorter, and softer than spruce 

 fiber, (3) The yield in paper and pulp per cord of wood is less 

 than in spruce. 



Under present methods of cutting, balsam fir is increasing 

 at the expense of red spruce in the second growth throughout the 

 entire range of the two species. The fir grows much faster 

 throughout its whole life than the spruce, but is shorter lived and 

 reaches maturity very much sooner. The fir should be cut at an 

 age of from 100 to 125 years, while spruce as it now grows in 

 natural forest should be cut at an age of from 175 to 200 years. 

 The annual increment per acre of balsam over its entire range 

 varies from one-sixth to one-third of a cord. 



Selection cutting in small groups is recommended as the best 

 silvicultural system for balsam. The natural reproduction of both 

 spruce and balsam is assured under this system, with the pos- 

 sibility of increasing the proportion of spruce in the new stand. 



S. J. R. 



Tyloses: Their Occurrence and Practical Significance in Some 

 American Woods. By Eloise Gerry. Reprint Journal Agricul- 

 tural Research. U. S. Department Agriculture Vol. i. No. 6. 

 1914. Pp. 445-470- 



This paper embodies the results of a careful study of a con- 

 siderable number of specimens of both hardwoods and conifers 

 with reference to tyloses. Emphasis is laid on the previously 

 known fact that tyloses may occur in the sap wood of all species 

 in which they occur in the heartwood, sometimes in the outer- 

 most rings near the bark. 



Attempt to explain the relation of tyloses to the properties of 



