1 8. 



The journal of Heredity 



most common species.'' An account 

 f)f the ceremonial and medicinal uses 

 of the \arious species in both the Okl 

 and the New World will ajipear in the 

 forthcominji Annual Rep)ort of the 

 Smithsonian Institution. 



In recent years certain yarieties of 

 the Jamestown weed {Datura stramon- 

 ium) have been used in the study of the 

 I)henomena of heredit\- and mutatitms. 

 All of the species are admirabh- 

 adapted for experiments in cross- 

 pollination. The anthers of the flowx^r 

 chosen for the female parent can be 

 remoyed easily before their dehiscence 

 and the flower coA'ered before the 

 corolla unfolds. Pollen can be obtained 

 with ecjual facility- from the covered or 

 unfolded flower chr)sen as the male 

 parent and applied U) the stigma of 

 the emasculated Hower. By this simple 

 method white-tlowered and purple 

 lorms, and forms with prickly and 

 with smooth capsules can readily be 

 crossed. Results of experiments of 

 this nature made by Miss K. R. 

 -Saunders confirmed in a most striking 

 manner the ctniclusions arri\'ed at by 

 Mendel relating to inheritance." 



In the summer of 1916 the WTiter 

 collected specimens of purple flowered 

 Datura stramonium growing at Round 

 Hill, Virginia, some of which bore 

 unarmed as well as prickly pods upon 

 the same plant. A comparison of the 

 former with specimens of the so-called 

 Datura inermis showed them to be 

 identical, while the prickley pods were 

 like those of the j)urple-tiowere<l Datura 

 tatula and the white-Howered Datura 

 stramonium. 



In July 1916, seeds bearing the label 

 "Datura inermis," received from F. A. 

 Miller of the Kli Lilly Company, 

 Indianapolis, were i)lante<l in the drug 

 garden at Arlington by Dr. .Stf)ckberger 

 of the Bureau of Plant Industry. 

 Plants of four distinct forms were the 

 result, all of which were collected and 



photographed b>- the writer. The most 

 abundant, with reddish-jnirple stems, 

 la\ender-colored corollas, dark \iolet 

 anthers, and upright, prickly capsules, 

 was identical in appearance with the 

 form commonly called Datura tatula. 

 Next in abundance, occurring in about 

 equal numbers, were white-Howered 

 plants with prickly capsules like 

 the typical Datura stramonium and 

 hnender-colored plants with smot)th, 

 or unarmed, capsules; and least abun- 

 dant of all was a form with white 

 flowers and unarmed capsules, identical 

 in all respects with Datura inermis. In 

 Figure LS, No. 1 shows armed capsules of 

 the purple-flowered form commonly 

 called Datura tatula: No. 2, pods of the 

 typical white-flowered D. stramonium; 

 No. 3, armed and unarmed piods of 

 of purple-stemmed, Uuender-flowered 

 f)lants; and No. 4 the green-stemmed, 

 white-flowered form with unarmed 

 capsules usually called Datura inermis. 

 The evidence offered by the relative 

 abundance of the various forms here 

 shown corroborates the results of the 

 experiments of Miss F. R. -Saunders 

 already referred to. Of the antagonis- 

 tic color characters the Aiolet was 

 dominant and the white-Howered form 

 recessive, and of the contrasted capsule 

 forms the prickly one was dominant 

 and the unarmed recessive." Very 

 similar results were presented in March 

 1917, by Blakeslee and AAery in the 

 form of a living diagram showing the 

 average results of a dihybrid cross 

 between the purple-flowered, purple- 

 stemmed Datura stramonium tatula 

 armata (PAr) and the white-Howered, 

 green-stemmed Datura stramonium 

 inermis (Win). In the latter case all 

 the first generation hybrids had purple 

 flowers and prickK' pods, while in the 

 sectmd generation there were 9 purple 

 armed, -S wliitc- armed, and -^ purple 

 imarmed, and 1 white unarmed, in 

 perft'ct conformity with Mendel's law." 



6 Safford, \V. !•:., Synopsis of the Genus Datura. Journ. Wash. Aiacl. 11: 17.? l.H<>, 1«>21. 



• See Hateson, \\ ., and Saunders, K. K., Experimental Studies in the Physiolony of Heredity; 

 in Reports of the Hvolution Comniittee of the Koyal Society of London 1 :21, 1902. 



' See Hateson, W., and Saunders, H. K., Kxperiniental Studies in the Thysiolo^y of Heredity, 

 in Reports of the Evolution Committee of the Royal Society of London 1 :21. 1902.' 



" HIakeslee and .Avery, Adzuki Ik-ans and Jimson Weeds, in Journ. Hered. S:12.S I.^I. 1917. 



