282 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1915. 



extract of the lieartwood in the larger phials, also in tap water con- 

 taining a small percentage of lime. The outer phials are repre- 

 sented with the light shining through them; the inner ones, against 

 the black background, display the fluorescence, as seen by reflected 

 light. 



Plate 5 is a colored drawing by Mrs. R. E. Gamble of two phials 

 containing an extract of Eysenhardtia wood in distilled water, made 

 slightly alkaline by the addition of a little carbonate of sodium. 

 The flask against the dark background is illuminated by light com- 

 ing obliquely from the left; the other flask is shown against the light, 

 with the surface of the deep amber-colored extract bounded by a 

 bluish circle. 



BOTANICAL DESCRIPTION. 



The plant positively identified as yielding the lignum nephriticum 

 mexicanum of Hernandez and Robert Boyle may be described briefly 

 as follows (see pi. 3) : 



Eysenhardtia polystachya (Ortega) Sargent. Silv. N. Am. 3:29. 1892. (Escl. 



Texas references). 

 Viborquia polystachya Ortega, Hort. Matr. Dec. 5:66. pi. 9. 1798. 

 Eysenhardtia amorphoides H. B. K. Nov. Gen. et Sp. 6 : 494. pi. 592. 1823. 

 Varennea polystachya (Ort.) DC. Prodr. 2:522. 1825. Oliva, Lecc. Farm. 2: 



429. 1854. 



An erect, sweetly aromatic shrub or small tree, glandular-punctate, 

 with spreading, recurved branches. Leaves even-pinnate or odd- 

 pinnate, with numerous small opposite or alternate stipellate leaflets ; 

 leaflets oval, or oblong-elliptical, entire, usually decreasing in size 

 toward the extremity of the rachis, the terminal one of odd-pinnate 

 leaves often obcordate, the others rounded or slightly retuse at 

 the apex and often terminating in a short acumen, pubescent when 

 young, sometimes becoming glabrate, usually punctate with glandu- 

 lar dots on the lower surface. Flowers fragrant, small, white, turn- 

 ing yellow in drying, borne in terminal densely spicate racemes; 

 pedicels subtended by a lanceolate deciduous bracteole, short and 

 slender, often reflexed at length, but sometimes ascending or widely 

 spreading; calyx glandular-punctate, 5-toothed, persistent; corolla 

 scarcely at all papilionaceous, composed of 5 nearly equal unguicu- 

 late petals; the standard slightly broader than the wings and keel, 

 emarginate, carinate, with involute margins ; stamens 10, diadelphous, 

 the superior one free, the filaments of the others united into a tube ; 

 ovary subsessile, oblong, compressed, terminating in a slender stjde, 

 somewhat longer than the stamens, geniculate and glandular below 

 the apex; stigma introrse. Legume very small, oblong, compressed 

 flat, subfalcate or almost straight, subtended by the persistent calyx 



