Periodical Literature 95 



until a maximum is reached, after which it decreases toward the 

 top." It is pointed out that this maximum occurs higher from the 

 ground in rings nearer the bark. 



3. Study of an eccentric section of White pine failed to indicate 

 any close relation between ring width and tracheid length. The 

 same was true in the Longleaf pine. 



4. Tracheids in the rothholz portion of a ring were consistently 

 shorter than those in the zugholz, in the case of an eccentric stump 

 of White pine. 



As a result of these variations, the care that must be exercised 

 in using "average fibre length" for identification purposes is 

 emphasized. 



From a study of one White pine. Miss Gerry obtained the 

 following results: (1) The shortest tracheids were found near the 

 pith, with an irregular increase in length from the centre outward; 

 no constant length was obtained. (2) A tendency toward an 

 increase in average tracheid length was apparent from butt toward 

 top for about two-thirds the height of the tree. These two results 

 agree with the foregoing investigation. (3) No relation could be 

 determined between tracheid length and the strength values of 

 the wood. The above findings are based on 6,600 measurements 

 from sixty-six specimens. 



From 2,600 measurements on twenty specimens (Longleaf pine 

 and Douglas fir) the general range of variation in tracheid length 

 was not found to be greater within the species than in the individual 

 tree. The longest elements were found in the earliest spring wood, 

 with a gradual decrease to the last formed layers of the ring. 



The relationship of these findings to wood pulp is noted. 



J. H. W. 



Some Observations on the Variation in Length of Coniferous "Fibres." Pro- 

 ceedings Society of American Foresters, IX, No. 4, 1914, pp. 522-527. 

 Fiber Measurement Studies. Science, 29 January, 1915, p. 179. 



Of North American conifers, the species 

 Classification of Abies are probably the most troublesome 

 of Firs to the forester to distinguish. This con- 



spectus of the genus, by Mr. Lamb of the 

 U. S. Forest Service, is accordingly very timely. 



It is pointed out that color of foliage and cones, and shape and 

 size of cone scales, are unreliable, and that the form of the bract 



