Books and Current Literature. 



187 



themselves very differently. The promptness of adjustment 

 observed leads the writer to conclude that plants of cold and 

 temperate climes may even be able to keep pace with the ad- 

 vancing cold of autumn months by a gradual lowering of the point 

 at which death by freezing takes place. 



Kraus, in a recent publication of the Physical-Medical 

 Society of Wurzburg, discusses certain questions of soil and cli- 

 mate arising in a study of limestone soils. With a different 

 amount of lime goes hand in hand a very different structure of 

 soil, and as a result of this the water content and temperature 

 of the soil are different. Soils containing a high percentage of 

 lime have less capacity for water and a higher temperature, 

 while those with less lime are moister and cooler, so that in these 

 soils highly important physical factors are present which ap- 

 parently render it quite unnecessary to assume chemical action 

 as a factor determining the nature of the plant covering. But 

 these physical factors are in turn greatly modified by a number 

 of conditions. Soil temperature varies with aspect and altitude, 

 and water content is influenced by the fineness or coarseness of 

 the soil, while, again, the drier the soil the higher does its tem- 

 perature rise (in sunlight). " All in all, the soils examined present 

 an endless variety physically and chemically, and the origin and 

 continuance of the many plant forms growing on them is to be 

 understood by reference to this variety." 



From a review by C. H. Ostenfeld of Wesenberg-Lund's 

 important work under the title Plankton Investigations of the 

 Danish Lakes the following abstract is presented of the author's 

 summary of present knowledge of the fresh water plankton of 

 the earth, its conditions of life and forms of adaptation. 



The plankton of different geographical areas is analyzed 

 and characterized in part as follows: 



1. The arctic fresh water phytoplankton is very poor, and 

 there is a great mixture of littoral and pond forms. 



2. The phytoplankton of the north European lakes is 

 richer. Diatoms are abundant; Desmids are also characteristic, 

 and Flagellates are important. 



3. The Baltic fresh water phytoplankton is very rich. 

 Myxophyceae are present in enormous quantities; Diatoms occur 



