178 Notes on Indian Botany. 



that M. Choisy has shown it deserved, and their error is easily 

 traced to too rapid generalization. Loureiro must have exa- 

 mined a species with a 4-celled fruit, and took it for granted all 

 the others had the same structure. Roxburgh on the other 

 hand, when drawing up the character of his genus Lettsomia, 

 seems to have had a species before him with a 2-celled 

 ovary, and assumed that all the other species with baccate 

 fruit had likewise only two cells. He consequently associated 

 under that character many species with 4-celled ovaries, and 

 only two or three having them 2-celled. M. Choisy, in the 

 course of his examinations, met with some species having four 

 cells, others having two cells ; of the former he has constituted 

 the genus Rivea, of the latter his genus Argyreia. But 

 falling into the same error as Loureiro and Roxburgh, he 

 has generalized where he should have dissected, and has 

 thereby been induced to bring together, under his essential 

 generic character " ovarium 2-loculare," numerous species 

 having ovarium 4-loculare. 



With a view to the correction of these blunders, with the 

 least amount of inconvenience to the science, I propose re- 

 taining all the three genera, which can be very well done 

 by merely slightly altering the character of Rivea, and leav- 

 ing the other two as defined by their original founders. 

 For example, Choisy gives to Rivea a capitate or lamelliform 

 £-lobed stigma and 4-celled ovary: I propose substituting 

 the word linear for capitate, and referring all Convolvula- 

 ceous plants having indehiscent fruit, a 4-celled ovary and 

 linear, cylindrical, or lamelliform stigmas, to Rivea, those with 

 4-celled ovaries and capitate 2-lobed stigmas, to Argyreia, and 

 lastly, those having 2-celled ovaries and capitate 2-lobed 

 stigmas, to Lettsomia. With this modification, Rivea stands 

 in exactly the same relationship to Argyreia, that Convol- 

 vulus does to Ipomcea, while Lettsomia forms the transition 

 from Argyreia to Ipomcea, having the indehiscent fruit of the 

 one, and the ^-celled ovaries of the other. 



