IAnnals N. Y. Acad. Sci., Vol. XVIII, No. 6, Part II, pp. 181-263. 11 May, 1908.1 



THE NORTH AMERICAN SPECIES OF THE GENUS IPOM(EA.» 

 By Homer Doliver House, B. S., M. A. 



I^^^RODUCTION. 



A comparative study of specimens of the ConvolvulacecB, represerrting 

 the species placed by Linnaeus^ in Ipomcea and Convolvulus, shows that 

 the two groups as there constituted, are far from homogeneous. The type 

 of Convolvulus is Convolvulus major albus, Toumefort, pi. 17 = (Convolvulus 

 sepium L.). The species included in Ipomoaa by Linnaeus do not accord, 

 except in part, with the diagnosis given by him in the Genera Plantarum 

 (1737), where it is stated that the stamens are exserted, and pi. 39 of Toume- 

 fort' is cited. This is Quamoclit Joliis tenuiter incisis & pinnatis (=Ipo- 

 mcea quamoclit L.). Under most circumstances this would establish it as 

 the type of the genus, but it must be remembered that the genus Quamoclit 

 was an accepted and valid genus before Linnaeus called it Ipomcea and the 

 genus has since been restored to generic rank by Moench.^ In the 5th. 

 edition of the Genera Plantarum (1752), the Toumefort reference to pi. 39 

 is still retained, with the addition of "Voluhilis Dill. Elth. 318." The 

 first species figured by Dillenius under Volubilis is V. zeylanica pes-triginus, 

 pi. 318. f. 4il' (=Ipomosa pes-triginus L.) 



In deference to historical usage and long continued uniformity, the 

 writer does not believe it necessary to restrict Ipomcea to the group of species 

 typified by Ipomcea quamoclit L., but is inclined to accept the species first 

 figured by Dillinius under Volubilis, if it is necessary to designate a t^-pe 

 for the genus Ipomcea. Without doubt the plant of greatest economic im- 

 portance is Ipomcea batatas (L.) Lam. but as that was placed in Convol- 

 vulus by Linnaeus and was known as Batatas * in pre-Linnaean literature, 

 it has nothing to recommend it as an acceptable type of the genus. If /. 



1 Presented in abstract to the Academy at the regular meeting on 9 March 1908. Manu- 

 script deUvered to Secretary 10 March, 1908. 



2 Species Plantarum, 1753; ed. 2, 1762-63. 



3 Institutiones rei Herbarise, 1700. 



* Rumph. Amb. 6: 367. pi. 130. 1750 

 sMoench, Meth. 453. 1794. 



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