284 GEOGRAPHICAL DISTRIBUTION OF PLANTS. 



out on approaching the south end of Lake Winipeg. Others 

 go a degree or two further north to the banks of the Sas- 

 katchewan, about Cumberland House, and there make 

 their last appearance : among these are the ashes, elms, 

 and maples. Some which are not seen beyond that locality 

 on the canoe route, go three or four degrees further north 

 on the western side of the prairies, in the sheltered valleys 

 of the Rocky Mountains. In these valleys also the lamented 

 Drummond found a considerable number of the species of 

 the Pacific coast, their range not being cut short by the 

 dividing ridge, but being seemingly more effectually limited 

 by the dry prairies. It is unfortunate that the vertical 

 limits of the species gathered by Drummond in the moun- 

 tains were not noted, as a careful list containing that 

 element, and which no one was more able than he to make, 

 would have conveyed much information with respect to the 

 distribution of plants. The statistical enumeration of the 

 mountain species, collected between 52° and 57°, in the 

 subjoined table evidently contains a mixed flora; some 

 families having an arctic, almost a polar character; others a 

 subarctic, or almost temperate one. 



LIST OF TREES AND SHRUBS.* 



RanunculacejE. — Clematis virginiana is common to Oregon, 

 the eastern United States, and Canada, and extends northwards 

 to the Saskatchewan. 



Berberide^e. — Berberis vulgaris has been found in Canada, 



* I am indebted to Dr. Asa Gray for some valuable information 

 respecting the range in the United States of some of the trees in the 

 following list. The Northern States referred to in the list extend 

 from New England to Wisconsin, and south to Ohio and Penn- 

 sylvania, inclusive. 



