114 LfiA^LMS. 



E. NUTTALLii. Kydb. Fl. Mont, under Roripa 

 K. AiPiifA. Eydb. 1. c. " " 



R. WALTBRi. Ell. Sk. under Sisymbrium. 



R. COLUMBIAE. Howell, Fl. under Roripa. 

 R. PACiEioA. Howell, 1. c. " " 



Segregates of the Oenus Rhus. 



No taxonomic problem is easier, no fact more thoroughly 

 established, than the identity of the original species, i. e., the 

 type species of the genus Rhus ; because during more than a 

 dozen centuries before even Tournefort, the species was but one, 

 and that familiar to all writers about plants as the variously 

 useful shrub of the whole Mediterranean region commonly 

 called Rhus, but also long before Linnaeus written of under the 

 binary name of Rhus coriaria, which name he also adopted. 

 The genus was all this while supposed to be monotypical ; 

 Rhus coriaria, the only Rhus. This fact is so easily apparent 

 in bibliography, that there is no room for any controversy as to 

 what is the type of the genus ; and neither Tournefort nor 

 Linnaeus, with the genus in view, could well have done otherwise 

 than they did in placing it first in the list of species ; placing 

 it as the type. 



In the seventeenth century the genus received two indubitable 

 accessions from North America in the shrubs now known as 

 Rhus hirta and R glabra. Nobody questioned or doubted that 

 these were of that genus. But along with these importations 

 from our shores came the Poison Ivy ; a type which no author- 

 ity did at first, or for a long time after, think of as possibly to 

 be associated with Rhus congenerically. 



Tournefort, before the end of the seventeenth century, pro- 

 posed for the two forms known to him the rank of a genus, 

 which he very fitly named Toxicodendron. Linnaeus suppressed 

 the genus ; but Philip Miller promptly restored it ; and several 

 more since Miller's time have insisted on its validity as a proper 

 genus, so that now it bids fair for permanent recognition in the 

 taxonomy of coming years. 



