PERIODICAL LITERATURE. 

 In Charge : 



Botanical Journals R. T. FiSHER 



Foreign Journals --B. E. Fernow, R. Zon, F. Dunlap 



Propagandist Journals H. P. BakER 



Trade Journals F. Roth and F. J. Phillips 



FOREST GEOGRAPHY AND DESCRIPTION. 



Mr. E. N. Transeaii furnishes a very in- 

 Forest Centers teresting paper on zonal forest distribution 

 oj in Eastern America based not on mere 



Eastern America description but on ecological and evolu- 

 tionary considerations. Instead of basing 

 his zones like Merriam on the single factor of temperature, he 

 secures his basis, much more rationally for floral forms, on a 

 combination factor, namely, rainfall-evaporation ratios, the 

 nearest approach to what the reviewer has claimed years ago as 

 the principal factor in the distribution of arborescent forms, the 

 transpiration factor. In a paper before the Michigan Academy 

 of Sciences, (March 15, 1905), on climatic centers and centers of 

 plant distribution, he points out, as have others before him, that 

 the distribution of plants generally is centric rather than zonal, 

 as Merriam has it, and that, by combining the figures for rain- 

 fall and evaporation, at least four climatic factors, having by 

 necessity a powerful influence on water relations and thereby on 

 distribution of plants, could be utilized to explain these centers. 

 The ratios found by dividing mean annual rainfall by the depth 

 of evaporation at the same station, percentically expressed, were 

 used to construct a climatic map. This showed at once a re- 

 markable coincidence between its divisions and those giving the 

 lines of distribution, not only of grassland, prairie, open forest 

 and dense forest regions, but also of forest types, namely, the 

 North Eastern conifer forest center with a rainfall-evaporation 

 ratio of between 100 to 200 per cent ; the deciduous forest center 

 with a ratio between 100 and no; the south eastern conifer 

 center with a ratio of no per cent ; the great plains marked by 

 an amount of rainfall equal to between 20 to 60 per cent, of the 

 evaporation ; and the prairie region with a ratio of 60 to 80 per 



