286 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1915. 



GEOGRAPHICAL DISTRIBUTION, 



The genus Eysenhardtia is confined to xVmerica. Its range ex- 

 tends from Texas and Arizona on the north to Guatemala on the 

 south. On the elevated plateau of northern Mexico it usually grows 

 as a shrub about 2 meters high, in southern Mexico as a tree 6 to 8 

 meters high, yielding wood wdiich is valued for cabinet purposes. 

 It is probably this wood which Padre Cobo had in mind, when he 

 described the " arbol de la immortalidad ; " and, as the wood resem- 

 bles lignum-vitae, it is possible that the latter suggested the name 

 wdiich Cobo applied to it and led to its incorrect identification as 

 a species of Gnaiacum, which appears in Dragendorff's Heilpflanzen. 

 Not far from Mexico City, on the pedregal, or lava beds, a low form 

 with small pubescent leaves occurs, which may possibly prove to be a 

 distinct species. 



In the Herbarium of the United States National Museum are 

 specimens of Eysenhardtia pohjstacliija from the Mexican States of 

 Sonora, Chihuahua, Nuevo Leon, Tainaulipas, San Luis Potosi, 

 Coahuila, Aguascalientes, Jalisco, Guerrero, Oaxaca, and Michoacan. 

 The plant also grows in the State of (hianajuato (according to 

 Duges), on the volcanic slopes of the Nevado of Colima near the 

 Pacific coast, and on Orizaba, near the Gulf coast. Specimens grow- 

 ing on the high watershed between Chilapa and Tixtla, in the State 

 of Guerrero, were collected by Mr. E. W. Nelson, of the U. 

 S. Biological Survey (No. 2159), and in the State of Oaxaca at 

 elevations of 1,500 to 1,800 meters, usually on the slopes of deep 

 barrancas. It also occurs in Jalisco, on the sides of the great bar- 

 ranca of Guadalajara, where it was collected by C. G. Pringle (No. 

 8762 and No. 9752), the barranca of Mochitiltic, cited by Oliva ; and 

 between Guadalajara and Bolailos, where it was collected by Dr. 

 J. N. Rose (No. 3734). On a herbarium specimen collected by Lan- 

 glassee (No. 226) in the State of Michoacan, at the station of La 

 Junta, the tree is described by the collector as an " arbre an tronc 

 elance ; bois, recherche pour ebenisterie, produit une teinture bleue." 



A photograph of the specimens from Tamaulipas described in this 

 paper is shown on plate 3 (opp. p. 280) and the wood Avith its in- 

 fusion on the colored plate 4. 



STRUCTURE OF THE WOOD. 



Microscopic sections of the wood of Eysenhardtia polystachya 

 were made at the writer's request by Dr. Albert Mann, plant mor- 

 phologist of the Bureau of Plant Industry, and by Mr. C. D. Mell, 

 recently attached to the Forest Service as assistant dendrologist, now 

 attached to the Bureau of Chemistry. Dr. Mann found the heart- 

 wood to be extremely compact, heavily lignified, and impregnated 



