No. 543] 



NOTES AND LITERATURE 



171 



remains that at present the western forest is composed in the 

 main of a great variety of coniferous trees adapted to dry sum- 

 mer conditions, while the eastern forest is distinguished by its 

 great richness in deciduous trees adapted to a humid summer 

 climate. Close to the retreating line of the forests, there pre- 

 sumably followed a belt of arctic vegetation clinging to the edge 

 of the advancing glaciers. 



With the retreat of the glaciers the plants advanced north- 

 ward again, and the present distribution was finally established. 

 Owing to the much greater altitude of the western mountains, it 

 is especially upon these that we find a true Alpine flora, the more 

 or less changed remnants of the arctic vegetation forced south- 

 ward by the advancing ice sheet. It is true that a few arctic 

 plants, like the Greenland sandwort, occur upon the highest 

 peaks of the Appalachian system, but the number of these is com- 

 paratively insignificant when compared with the rich and beauti- 

 ful Alpine flora of the Canadian Rockies and the Cascades. 



At the close of the glacial epoch the distribution of the plants 

 was practically as at present, the most marked features being the 

 eastern and western forest areas and the great open region of 

 the great plains. 



Part four deals with the floral regions as they now exist in 

 North America. Probably most botanists will feel that the 

 weakest feature of this account of the flora of North America is 

 its lack of proportion. While the relatively uniform flora of the 

 Atlantic half of the continent receives over 150 pages, the Rocky 

 Mountain flora is dismissed with 23 pages, and the extraordi- 

 narily varied and interesting flora of the Pacific Coast with less 

 than fifty. This no doubt is to be explained by the author's 

 very intimate acquaintance with the flora of the Atlantic states, 

 and his evidently very casual observations at first hand upon 

 that of the western third of the continent ; but he has not shown 

 the best judgment in the selection of topics for discussion, deal- 

 ing at great length with relatively very unimportant regions. 

 Nearly as much space is given to a discussion of the pine-barren 

 flora of the Atlantic Coast states as to the whole of the Pacific 

 Coast from Alaska to Mexico. The multiplication of details 

 in the discussion of the floras of small and unimportant areas, 

 results in a general sense of confusion, and one is often at a loss 

 to see the bearing of many of the detailed descriptions of local 

 floras upon the larger problems. It is a pity that the abundant 



