No. 543] NOTES AND LITERATURE 



173 



arctic regions of the Atlantic and the Pacific, many striking 

 genera including the giant Kelps being quite unrepresented on 

 the Atlantic side of the continent. Harshberger thinks that 

 this points to these two regions as being distinct centers of de- 

 velopment and distribution, and it may also show that some of 

 the extraordinary Kelps of the Pacific Coast may be relatively 

 recent developments. 



South of the arctic zone is a sub-arctic forest zone, also of 

 very similar composition throughout its whole extent from Labra- 

 dor to Alaska. This forest is largely composed of Conifers, the 

 predominant trees being White and Black Spruce, Balsam-Fir, 

 Tamarack and Scrub pine. 



With the Conifers are associated Aspens, Balsam Poplars, Wil- 

 lows, Alders and Birches. Swamps and peat bogs abound and 

 in these as well as in the forest itself grow many attractive 

 shrubs and herbaceous plants. Ericaceous shrubs are especially 

 abundant, Ehododendron, Kalmia, Ledum, Vaccinmm, etc., as 

 well as wild Eoses, species of Rubus and Ribes, etc. In the 

 Sphagnum bogs, especially in the eastern portions, are found 

 Pitcher plants, Sundew, and several beautiful Orchids. A con- 

 siderable number of species, e. g., Pyrola rotundifolia, lAnnaa 

 borealis, Cornus Suecica, are identical with Old World species, 

 and most of the genera, although not the species of trees, are the 



To the southward of this uniform forest zone a greater diver- 

 gence in the floras is noted, and within the l nited States the 

 character of the vegetation changes radically as one proceeds, 

 from the "Atlantic seaboard westward. 



The whole of the eastern third of the United States may be 

 said to comprise one great phytogeographical area, although of 

 course there are certain regions where the flora has a more or less 

 marked type of its own. Nowhere within this area are the 

 mountains of sufficient elevation to form barriers against the 

 ready migration of plants, and the whole region is one of abun- 

 dant rainfall. The whole area being continuous, the result is a 

 very uniform flora, when contrasted with the Pacific side of the 

 continent. Many species of trees, e. g., Elms, Oaks, Walnuts, 

 Hickories, etc., occur throughout the range and the same is true 

 of very many herbaceous plants. It is true that the number 

 of species is much greater in some parts than others, owing o 

 more favorable conditions of soil and temperature, but there are 



