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JOURNAL OF FORESTRY 



the same stick as that ilhistrated in figure 9. In this one the vessels 

 occupy the major portion of the field, and consequently augment the 

 tendency to brashness. The fibers in addition to being few in number 

 are also thin-walled. The other structural features do not differ to 

 any large extent from those already mentioned and consequently do 

 not deserve further consideration. 



Table 2 will aid in clarifying the relation as between structure and 

 brashness. The specific gravities show a proportion similar to that 

 mentioned in Table 1, and the percentage of fibrous tissue and the 

 thickness of the fiber walls shows a like proportion of roughly 3 to 1. 

 In both, the diameter of the fibers is nearly equal, and in this way 

 follows the general rule of the constancy of cell size in species. The 

 other measurements mentioned are not as important, and the record 

 in the table will serve for comparisons but need not enter into the 

 discussion. 



Table 2. — Liriodendron tulipifera L. Measurevients in millimeters. 



Figure 7 shows diagramatically one of the strong fibers of the tulip 

 poplar. The shaded portion represents the relative thickness of the 

 wall and the width of the lumina. Modifications of the ends of the 

 fibers which serve to increase cohesion are shown in which one is forked 

 and one sawtoothed. 



An interesting development in relation to the validity of fiber length 

 in reference to brashness was shown by a specimen not included in the 

 table where a specific gravity of .46 was associated with a fiber length 

 of 1.34 mm., or in fact, shorter than they were in the light weak wood 

 mentioned in Table 2 where the relation was as .31 to 1.49. 



In Liriodendron, therefore, mutability in strength appears to be 

 closely related to the proportion of fibrous and conducting tissue, the 

 thickness of the fiber walls, and the volume occupied by the vessels 

 and rays. Tulip poplar wood in general shows great variation in its 



