482 ^[EMOIRS OF THE NEW YORK BOTANICAL GARDEN 



Nothing in the East corresponds to the characteristic and con- 

 spicuous Odostemon {Berberis) Aquifolium and Pachystima Myr- 

 sinites of the Rockies, and Echinopanax horrida is found only as 

 a waif at the western end of Lake Superior. The conspicuous genera 

 Castilleja, Peutstemon, A quilegia, Arnica, represented by numerous 

 species in the Rockies, are poorly represented in the Canadian 

 fiora. Dr. Alerriam has made the statement,' "In a communica- 

 tion already referred to, I stated the conclusion that the commonly 

 accepted division of the United States into Eastern, Middle, and 

 Western Provinces had no existence in nature and that the whole ex- 

 tra-tropical North America consists of but two primary life regions, 

 a boreal region which is circumpolar, and a Sonoran or Mexican 

 Tableland region which is unique." These statements are far from 

 correct when the plants are considered. It may be that the animals, 

 which are less dependent on soil, moisture, and other conditions, and 

 are endowed with locomotion, might be the same in the western part 

 of the northern woods (Hudsonian and Canadian Zone) and the 

 forested region of the Rockies, but as far as the flora is concerned 

 it is not the same. Though the two regions touch at the head- 

 waters of the Athabasca River and north, there is not a single of 

 the characteristic forest trees in common. The only tree of 

 general distribution common to the two regions is, as mentioned 

 before, the aspen, and some botanists, Tidestrom, Wooton and 

 Standley, etc., regard the western a distinct species, Popidus 

 aurea; and others, Daniels, etc., as a distinct variety. The 

 boundary line between the eastern woods and those of the Rockies 

 is UKjre distinct than between the different life zones of the Rockies. 

 Many sjjecies, as for instance the sage brush and several species 

 of poplars and willows, are found both in the Montane (Canadian 

 of Merriam) Zone and the Upper Sonoran. not to speak of all 

 that are common to Alerriam's Canadian and Transition or his 

 Transition and Upper Sonoran. 



If we compare the Montane Zone of the Rockies and ihal of 

 the Pacific (\)ast mountains, we find that they have many more 

 species in common. • This is due partly to the fact that the Cascades 

 and the Northern Rockies are connected by many mountain 

 ranges. Many of the Rocky Mountain plants ha\c migrated 

 into the Cascades, and several of those belonging to the Pacific 



' Sec Proc. Biol. Soc. Wash. 7: 5K. i«y2. 



