174 JOURNAL or THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 8 



purple is dominant and the white-flowered form recessive, and of the 

 contrasted capsule forms the prickly one is dominant and the unarmed 

 (inermis) recessive ; so that at one end of the series we have the so- 

 called Datura tatula and at the other the white-flowered "Datttra 

 inermis." This is discussed in the author's forth-coming paper, 

 "Datura, an inviting genus J or the study of heredity," to be published in 

 the Journal of Heredity. 



The tree daturas of South America have been segregated as a dis- 

 tinct genus under the name Brugmansia, chiefly on the score that they 

 have fleshy spineless indehiscent fruits devoid of a persistent expanded 

 calyx base; but the section Ceratocaulis is characterized by similar 

 fruits and may be regarded as connecting the tree daturas with the 

 section Dutra, in which the capsules are irregularly dehiscent and in- 

 clined or nodding, quite unlike the erect valvate capsules of the sec- 

 tion Stramonium. 



A study of the tree daturas shows that more than one species has 

 been included under certain specific names. Thus Datura arhorea of 

 Ruiz and Pavon and Brugmansia arhorea of Lagerheim are specifically 

 distinct from the true Datiira arhorea L-, based upon P^re Feuillce's 

 Stramonioides arhoreum, and the pubescent orange-flowered huantuc 

 of Ecuador, with sinuate woolly leaves, is also quite distinct from the 

 typical Datura sanguinea of Ruiz and Pavon, with which it has been 

 confused. 



The following systematic synopsis is part of a paper submitted by 

 the writer as a thesis for the degree of Doctor of Philosophy at George 

 Washington University. The remainder of the paper, illustrated by 

 numerous photographs of living plants, will appear in the forthcoming 

 Year Book of the vSmithsonian Institution. 



DESCRIPTION OF THE GENUS 



The genus Datura, established by lyinnaeus (Gen. no. 246) with Datura 

 stramonium as its type, belongs to the family Solanaceae and to the tribe 

 Datureae, which includes also the closely allied genus Solandra of tropical and 

 subtropical America. It may be characterized as follows: 



Calyx long-tubular, herbaceous, appressed to the corolla tube or inflated, 

 toothed at the apex or spathe-like and split down the side, in certain groups 

 circurascissile at the base, leaving a disk which enlarges like a shield or cup 

 subtending the fruit; in another group either disappearing entirely or per- 

 sisting like a husk which covers the lower part of the fruit. Corolla funnel- 

 shaped or trumpet- shaped, in certain species suggesting the corolla of a 

 Convohndus, the tube usually long and slender, the limb plicate and either 

 5-lobed with the lobes separated by sinuses, or circular or lo-angled, with the 

 margin between the 5 teeth entire or obtusely angled, the angles sometimes 

 cuspidate giving to the expanded limb the form of a lo-pointed star. Stamens 



