LIST OF TREES AND SHRUBS. 287 



It is a familiar shrub in the Northern States, but I have 

 not been able to ascertain its southern limit. The Vitis cor- 

 difolia or riparia, frost grape, grows, on the evidence of 

 collections made on my former journeys, as far north as the 

 south end of Lake Winipeg, on the 50th parallel. I did not 

 observe it on my late voyage, in which, indeed, I had very little 

 leisure to search for plants ; and if it actually grows in so high 

 a latitude, it does not produce edible fruit so as to attract the 

 attention of the residents, who could give me no information 

 concerning it. Together with the Vitis cestivalis, or summer 

 grape, it is common in Wisconsin and Minesota. Some of the 

 native American vines are cultivated in the eastern states ; and 

 the Isabella grape, a variety of the Vitis labrusca, has an agree- 

 able though peculiar flavour. 



Zantholace^e. — Zanthoxylum americanum, northern prickly 

 ash, and Ptelea trifoliata, the shrubby trefoil, grow in Canada 

 and "Wisconsin, where they seem to find their northern limit. 



CELASTRiNEiE. — Stciphylea trifolia, bladder nut ; Euonymus 

 atropurpureus, burning bush ; E. americanus, strawberry 

 bush ; and Celastrus scandens, inhabit Canada and Wisconsin, 

 but were not observed to the north of Lake Superior. E. atro- 

 purpureus crosses the continent to Oregon. 



Rhaiune^;. — Rhamnus alnifolius, alder-leaved buckthorn, 

 grows from Maine and Michigan northwards, to about the 58th 

 parallel. It is a low shrub, and is applied to no economical 

 purpose. R. purshianus is an Oregon plant, which extends to 

 Vancouver's Island and New Caledonia. Ceanotlms ameri- 

 caniis, New Jersey tea, ranges from Maine, Michigan, and 

 Wisconsin, to Canada West, but was not gathered by us to the 

 north of Lake Superior. The C. Icevigatus, a west-coast species, 

 which extends from Oregon to Vancouver's Island, seems to be 

 the only member of the genus that enters the British territory. 

 C. sanguineus is common in the valley of the Columbia, and 

 crosses the mountains to the upper tributaries of the Missouri, 

 forming one of the many instances of west-coast plants traversing 

 the dividing ridge to the eastern prairies, but not extending to 

 the eastern woodland districts. 



