OF ARTS AND SCIENCES. 363 



XXIV. 



CONTRIBUTIONS TO AMERICAN BOTANY. 

 By Asa Gray. 



Communicated March 13, 1886. 



1. A Revision of the North American Ranunculi. 



Almost half a century ago the North American species of Ra- 

 nunculus^ as then known, were hastily compiled for Torrey and 

 Gray's Flora, with very little knowledge of original materials; and 

 they have not been elaborated since. The following is a summary 

 of a recent painstaking study of them. 



§ 1. Batrachium, DC. Although the European forms or species 

 of this subgenus are numerous and difficult, only a few are known in 

 North America, and these still need investigation. 



We have among them a peculiar type, and our species may be pre- 

 sented in this form. 

 * Styles subulate, not longer than the ovary, introrsely stigmatose, 



sometimes for the whole lenojth : petals deciduous. 



-)— Submersed foliage capillary-multifid, in this country no other seen 



except far north and west : carpel-receptacle hairy. 



R. circinatus, Sibth. Known by its short and sessile leaves, of 

 rigid texture, forming an orbicular circumscription at right angles with 

 the stem. Here belongs R. longirostris, Godron, the original from St. 

 Louis. Sil)thorp's name is preferred to the slightly earlier R. di' 

 varicatus, which, as Hiern has made out, belongs to 7?. aguatilis, var. 

 trichophyllus. 



R. AQUATiLis, L., we should still keep as a collective species, with 

 the Linmean name ; the type of Linnaeus being the form heterophyUus. 

 This occurs in British America, and from North Alaska to California ; 

 but not a single specimen is known from the Atlantic United States. 

 Instead, we have everywhere 



Var. TRICHOPHYLLUS, — to keep up the earliest and most used 

 specific name for the whole series of forms, — with many subvarieties. 



