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JOURXAL OF FORESTRY 



a specific gravity of only .36 which in its turn is associated with a 

 summer wall thickness of .002, 19 per cent of ray tissue, and 20 per 

 cent of summerwood. The other measurements mentioned in the 

 table are not as significant, and need no further attention. 



Table 3. — Fraxiiius avurricana L. Measurctnents in millimeters. 



The amount of ray tissue having as it does a very definite bearing 

 upon the problem should not go unnoticed. \'ariation is very marked 

 in the white ash, as is shown in figure 10, a strong wood where 10 

 per cent has been differentiated for storage, and in figure 11 a weaker 

 one where the volimie reserved for such a purpose is about 30 per cent, 

 with its concomitant diminution of the fibrous elements and resistance 

 to stress. 



The rate of growth in ring-porous woods is of interest since it has 

 long been known that strength in hardwoods is more or less coincident 

 with rapidit}- of growth. The anatomical reasons for such a belief 

 are well shown in figure 8. which represents a cross-section of a sup- 

 pressed Fraxinus. It will be observed that of the entire year's incre- 

 ment over two-thirds of the area is occupied by the spring vessels and 

 short fibers, while the remainder is possessed by the small summer 

 vessels and thick-walled fibers. In those woods where growth has 

 been more rapid, the area reserved for conduction is about equal to 

 that shown in the print, while the increased width is added to the 

 stronger simimer portion. Even though in general increase in width 

 means increase in the number of summer fibers, it does not always 

 follow that such woods will be strong, since the fibers may be thin- 

 walled similar to those shown in figure 6. In the trade, ash of this 

 character is known as "pumpkin ash," a term by no means restricted 

 to the wood of Fraxinus profunda. 



Brashness in white ash woods, therefore, appears to be associated 

 primarily with a narrow summer growth, with thin fiber walls, with 



