TRUE MAHOGANY. 21 



potassium and sodium hydroxides. The wood when boiled in a weak 

 solution of the hydroxides yields a deep reddish-brown coloring 

 matter. 



Wood fibers occur usually in distinct radial rows, from a few to 12 

 or 15, Jbetween pith rays, and constitute the bulk of the wood. Near 

 the pores this regular radial arrangement is often disturbed by their 

 rapid growth. They are polygonal and have as a rule small lumina 

 (cell cavities). They vary from 0.84 to 2.268, averaging 1.315 milli- 

 meters in length, and are rarely more than 0.02 millimeter in 

 diameter. Wood fibers are often found that have delicate transverse 

 partitions (fig. 4, B), a character that has been frequently observed 

 in other woods belonging to this family of trees. True wood fibers 

 are sometimes mistaken for wood-parenchyma fibers, but they may 

 be distinguished from the latter by the very sharp-pointed ends and 

 the minute, simple, slit-like pits. The fact that the wood fibers in 

 mahogany are septate serves to distinguish true mahogany from a 

 great many of its substitutes. 



The cells in the outer part of the annual rings of growth are espe- 

 cially remarkable for their thickness and density. It is also notice- 

 able that the cavities of the wood fibers in the early wood of samples 

 from Florida and Cuba are larger than those formed later in the 

 season. The reason for this appears to be that the fibers with wide 

 cell cavities in the early wood serve as carriers of sap, and there is, 

 therefore, no need of large vessels for this purpose in the late wood. 

 This is evidently not the case in wood from British Honduras. In 

 wood of the latter type, which forms no such large cells in the early 

 wood, there seems to be greater need of large vessels throughout the 

 entire seasonal or annual layer of growth in order to transport the 

 large supply of water these trees require, because there is practically 

 no cessation in vegetative activity throughout the growth period. 

 The distribution of the large vessels is, therefore, regular through- 

 out. In the wood with large vessels the fibers have thinner walls, and 

 the quality of wood may be judged or predicted from such structural 

 characteristics. 



Wood-parenchyma' fibers (fig. 4, A h) occur usually near the ves- 

 sels and consist of from four to eight slightly elongated, thin-walled 

 cells. In transverse section these cells are polygonal in form; in 

 longitudinal section they are perpendicularly elongated and have 

 small round or oval pits on their radial and tangential walls. Where 

 they are in contact with vessels the pits are larger and not infre- 

 quently have a slight border. The individual cells contain an abun- 

 dance of dense brown coloring matter similar to that found in pith- 

 ray cells. A number of these fibers are made up of cubical cells with 

 very thin walls, each cell being filled with a small crystal of calcium 

 oxalate or calcium carbonate. These crystal-containing fibers are es- 



