BOOKS AND CURRENT LITERATURE 301 



ium, well known as absentees from calcareous soils, were found in 

 soil with 3.4 % of lime; Sarcothamnus scoparius was the only plant 

 found solely on soils free of lime. 



These results lead us to realize the wide diversity of the percentages 

 of line in calcareous and " non-calcareous" soils, and the ability of 

 the generality of plants to endure wide ranges of lime content. During 

 the growth of a single plant its root system encounters different percent- 

 ages of lime at different depths, and the percentage at a given spot 

 varies during the life of the plant. Almost the whole of the evidence 

 regarding the role of soil chemistry in determining the distribution of 

 plants, from Thurmann to the most recent writers, has been gathered 

 by purely observational methods in which the mineralogical character 

 of the underlying rock was the only criterion of the chemical nature 

 of the soil. While Kraus does not compel us to discard the distinction 

 of lime plants and silicious plants, he nevertheless makes it necessary 

 for us to greatly broaden our conception of them, and he places future 

 workers in this field under the necessity of using precise methods of 

 determination of the state of the soil. 



The work of Kraus on the climate of his area is also devoted -to an 

 elaboration of the differences which exist within very small space. He 

 discusses variations of soil moisture between wet and dry periods, be- 

 tween north and south slopes, between bare and leaf-covered soil, 

 as well as between different depths. Temperature is discussed chiefly 

 in connection with the relation of air and soil temperatures, and their 

 significance for plants, although vertical differences of temperature are 

 also discussed, and the temperature amid the foliage of plants. Humid- 

 ity and wind are also discussed, more briefly, the author having already 

 published results on a study of the wind in this area. 



Kraus's work on climate is not so thorough as that on soil, in which 

 lies the principal value of his paper. It helps, however, to emphasize 

 his contention regarding the differences of environmental conditions 

 which may be found within small compass. While this contention 

 needs little argument among those who have done outdoor instrumen- 

 tation, it is nevertheless one which has not been previously made in 

 botanical literature with such full supporting data. — F. S. 



