JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. 11 April 19, 1921 No. 8 



BOTANY. — Synopsis of the genus Datura.^ William E. Safford, 



Bureau of Plant Industry. 



A critical study of the genus Datura has revealed great confusion in 

 botanical literature in connection with the specific identity, as well as 

 the origin, of some of the most common species.- Some authors, 

 for example, call a certain species endemic in Mexico and northern 

 South America Datura metel; but the true Datura metel, described by 

 Linnaeus in the first edition of his Species Plantarum, is a species based 

 upon the Asiatic metel nut, or "jouz-methel," which was used as a 

 narcotic by the Arabs, Persians, and Hindoos long before the discovery 

 of America, and was described by Avicenna in the eleventh centur}^ 

 Forms of this species, differing from the type in color and in the re- 

 duplication of the corolla, have been set apart as a distinct species 

 under the name Datura fastuosa, while the white-flowered type itself 

 was rechristened Datura alba. Much of the confusion is due to the 

 treatment which this genus received at the hands of Dunal in the first 

 part of volume thirteen of De Candolle's Prodromus (1852), in which 

 the name Datura metel was transferred from the Asiatic plant above 

 mentioned to an American plant described in 1768 by Miller under 

 the name Datura innoxia. 



Conflicting statements regarding the origin of the well known James- 

 town weed [Datura stramonium L.) are frequently encountered.^ Cer- 

 tain authors declare it to be of Asiatic origin, although Linnaeus in 

 describing it states that it is American. Others assign the typical form, 

 with green stem and white flowers, to Asia, and the purple-stemmed 

 lavender-flowered form, commonly called Datura tatula, to America. 

 Still others have separated a variety with smooth capsules from the 

 typical prickly-fruited form under the name Datura inermis. Ob- 

 serN-^ations on growing plants show that both the white-flowered and 

 purple-flowered forms may bear either smooth or prickly capsules, in 

 some cases even on the same plant. Experiments in cross-breeding 

 have demonstrated that of the antagonistic color characters, the 



' Received March 14, 192L 



2 See Hemsley, Biol. Centr. Am. Bot. 2: 427. 1882. 



' See Robinson & Fernald, Gray's Manual ed. 7. 717. 1908. Brixton & Brown, 

 lUustr. Fl. ed. 2. 3: 169. 1913. 



173 



