114 LEAFLETS. 
R. NuTTALLU. Rydb. Fl. Mont. under Roripa 
R. ALPINA. Rydb. Le $ s 
R. WALTERi. Ell. Sk. under Sisymbrium. 
R. COLUMBIAE. Howell, Fl. under Roripa, 
R. pacitFica. Howell, Le Wé s 
Segregates of the Genus 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 Linnæus 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 
Linneus, 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. 
