FUSTIC WOOD! ITS SUBSTITUTES AND ADULTERANTS. 13 



The end cross walls are wholly absorbed, leaving an open passage 

 connecting the abutting segments. These end walls are usually 

 horizontal, though there are exceptions, especially in segments of 

 the largest vessels, which have more or less oblique ends, each with 

 an elongated pointed projection extending along the side of the next 

 segment above and below. 



The walls of the vessels have bordered pits. Where vessels are in 

 contact with wood-parenchyma fibers or pith-ray cells the pits are 

 arranged in groups, and although they are bordered, at least in the 

 walls of the vessel, a slight transition to large simple pits occasion- 

 ally occurs in the adjoining elements. The pit canals are round on 

 the outside of the vessel walls, but they gradually widen out laterally 

 on the inner walls of the vessels into slitlike canals which communi- 

 cate one with another. The small vessels, especially those resembling 

 tracheids, have markings on their walls similar to those of vessels; 

 spiral-like markings, such as are found in osage orange, are nowhere 

 present in this species. True tracheids have not been found in this 

 wood ; all elements with small cavities and bordered pits have simple 

 perforations, at least at one end, and are thus to be classed as parts 

 of vessels. 



Wood fibers 1 are arranged radially in regular rows. They have 

 exceedingly thick walls, the cavities being almost entirely obscured. 

 In the region of large pores, which by virtue of their rapid growth 

 exert considerable lateral pressure, the wood fibers and wood-paren- 

 chyma fibers are flattened radially; otherwise they are either circu- 

 lar, oval, or polygonal. Wood fibers vary in length from 0.65 to 1.18 

 millimeters, with an average of 0.939 millimeter. They are often 

 less than 0.02 millimeter in diameter, and are long acuminate at both 

 ends. The markings on the cell walls are indistinct, the pits being 

 simple, minute, and arranged in a single row, chiefly on the radial 

 walls. 



Wood-parenchyma fibers l are arranged in tangential bands forming 

 structures which contrast strongly with the bands of harder tissue 

 bordering on the outside and inside. In transverse section these ele- 

 ments are often twice as wide as the wood fibers, or about 0.04 milli- 

 meter, their walls much thinner, and their cavities relatively larger 

 and invariably filled with a parenchymatous substance easily soluble 

 in alkali. Wood-parenchyma fibers bordering vessels are generally 

 compressed either in radial or tangential direction; elsewhere they 

 are circular or polygonal. They are somewhat shorter than wood 

 fibers, and are composed of from 3 to 8 wood-parenchyma cells (more 

 often 3 to 5) having horizontal or sometimes slightly oblique cross 

 walls. The walls of these elements are marked on all sides by simple 



1 See description (fig. 1). 



