saffoed: lignum nephriticum 503 



and aluminum and iron hydroxides amounting to about 10 per 

 cent. 



The name vegasite^ is suggested for the mineral from Las 

 Vegas, the principal town of the county in which it Occurs. 

 Briefly, vegasite may be characterized as a mineral giving chemi- 

 cal reactions similar to those of plumbojarosite, but distinguish- 

 able by widely different optical constants. 



BOTANY. — Eysenhardtia polystachya, the source of the true 

 Lignum nephriticum mexicanum.^ William Edwin Saffoed, 

 Bureau of Plant Industry. 



INTRODUCTION AND HISTORY 



Among the wonderful products of the New World brought to 

 Europe shortly after the discovery of America was a Mexican 

 wood supposed to be efficacious as a diuretic and therefore called 

 lignum nephriticum. Water kept in cups of this wood and an 

 infusion of its chips in spring water had the remarkable property 

 of reflecting a blue color, though apparently colorless or yellow 

 when held up to the light in a glass receptacle. This led to the 

 experiments of Athanasius Kircher,^ in 1646, and afterwards 

 to the more systematic study by the Hon. Robert Boyle, in 1663, 

 which may be regarded as the first serious investigation of the 

 phenomenon now known as fluorescence.^ One result of Boyle's 

 work was to make fignum nephriticum a classic wood. Strange 

 to say, however, the botanical identity of the plant from which 

 this wood was derived has remained uncertain until the present 

 day. Though celebrated throughout Europe in the 16th, 17th, 

 and the early part of the 18th centuries, sacrcely a fragment of 



8 The "e" in the first syllable should be given the Spanish pronunciation: 

 like "a" in late. 



1 Based upon a paper entitled "The rediscovery of Lignum nephriticum," 

 read by the author February 2, 1915, at a meeting of the Botanical Society of 

 Washington. Published with the permission of the Secretary of Agriculture. 



2 "Of a certain wonderful wood coloring water all kinds of colors," in Ars 

 Magna Lucis et Umbrse, pp. 77 and 78. 1646. 



^ Boyle, Robert, Experiments and considerations touching colours, p. 203. 1664. 



