LIGNUM NEPHRITICUM — SAFFORD. 287 



with a peculiar substance which coiikl be called neither a resin nor 

 a gum, insoluble in water, and not breaking down in alcohol or 

 xylol. This substance is contained in pitted tracheae, or tubular 

 vessels, which in a cross section appear like pores either solitary or 

 in groups of two or three. Radial and tangential sections show the 

 pitted tracheae throughout their length either partly or entirely 

 filled with the resin-like substance, and they also show the medullary 

 or pith rays, which in the cross sections are quite inconspicuous. 

 .The annular lines of growth, however, are well marked in the cross 

 sections. 



The accompanying drawings (p. 288) were made by Mrs, Gamble 

 from photogi'aphs of sections of the wood of Eysenhardtla pohj- 

 stachya cut by Mr. C. D. Mell. Figure 4 shows a cross section of 

 the wood in which the annular lines of growth, «, the tracheae, 6, 

 either empty or containing the resin-like substance, and the inter- 

 vening wood parenchyma, c, are indicated. Figure 5 shows a ra- 

 dial section in which the pitted tracheae, ?>, either empty or con- 

 taining the resinoid substance, the intervening wood parenchj^ma, 

 (7, and the transverse medullary rays are shown throughout their 

 length. Figure G shows a tangential section in Avhich the tracheae, 6, 

 appear very much as in the radial section, but the medullary rays, c?, 

 are only seen in cross section between the tracheae and the mass of 

 wood parenchyma, c. 



SOURCE or ITS FLUORESCENCE. 



Experiments were made to determine the source of the fluorescence 

 of Eysenhardtla wood by Dr. Arno Viehoever, pharmacognosist of 

 the Bureau of Chemistry, assisted by his collaborators, Mr. C. O. 

 Ewing and Mr. J. F. Clevenger. The results olitained show that 

 the fluorescence is not inherent in the resin-like substance contained 

 in the pitted trachea?. This is quite insoluble in water, while the 

 substance which causes the fluorescence is freely soluble even in cold 

 water, as already stated. It is somewhat less soluble in alcohol and 

 scarcely at all so in chloroform and ether. Unfortunately the amount 

 of material available was too small to ol)tain with certainty the 

 fluorescent substance in crystalline form. 



The fluorescing power of the wood is so great that an extract of 

 one part of the wood in one hundred-thousand parts of water or al- 

 cohol, after having been made alkaline, showed a distinct fluorescence 

 in diffused daylight, and wlien diluted to a ratio of one to one million 

 a fluorescence could still be detected in the rays of a fluorescence 

 lamp. In very attenuate solutions the fluorescence is bluish ; in more 

 concentrated solutions it is distinctly yellowish green. 



Under a fluorescence microscope dry wood-sections showed a rather 

 uniform fluorescence with some very minute bright spots. Sections 



