A STUDY OF RHUS GLABRA 169 



distribution. It is almost local, occurring nowhere but in lower 

 and middle districts of the Carolinas and Georgia. 



Rhus lyphiua, the largest and most tree-like of our species, 

 ranges widely, at least when compared with R. pumila. It is cata- 

 logued for all the states from Maine to Georgia and Mississippi, 

 thence northward to Minnesota and the Dakotas, but is every- 

 where less common than R. glabra, and more particular than 

 either that or R. cofalliiia as to its environment. Everywhere 

 southward it is of the mountains or the hill country only, never 

 coming down to the lowlands or to the seaboard. Neither at 

 the northwest does it come out from its woodland habitat to 

 adorn the copses bordering the prairies where a subspecific ally of 

 R. glabra is so much in evidence. It seems to have little 

 adaptability to varying conditions other than those of heat and 

 cold ; though in this regard its adaptability is very marked. 

 The climate of Minnesota and the Dakotas, and that of Georgia 

 and Mississippi are extremely unlike as to temperature. Yet 

 between the Julius typhina of the most northerly locality and 

 that of the stations farthest southward, one does not discover 

 notable differences other than those of the size of the shrub and 

 the number of the leaflets. In other respects they seem to be 

 much the same ; so that the type is apparently one of a singular 

 degree of stability under somewhat varying conditions. 



Concerning R/ius glabra, the type species of the genus as to 

 North America, one may note first of all its nearly universal dis- 

 tribution. In this regard it is most unlike any of its congeners 

 here. From beyond the river St. Lawrence northward, down, 

 to the very shores of the Gulf of Mexico, its range is across the 

 continent. Within these parallels, into every floral region be- 

 tween the oceans, however different — excepting only that of 

 California — there enters that which, according to the books 

 and lists of plants, is Rhus glabra. 



There is no one species of tree or shrub of any continent 

 that really holds the geographic range which the books and lists 

 ascribe to Rhus glabra. By all the analogies of things there 

 ought to be several marked species or subspecies of this type in 

 the southern Appalachian region between Maryland and Ten- 

 nessee and Georgia ; another and an equally distinguishable set 



