Geographische Verbreitung, Reisen. 347 



1023) LeClere, J. A. and Yo der, P.A., Environmental Influences on the 

 Phvsical and Chemical Characteristics of Wheat. In: Journ. Agr. Res- 

 earch, Vol. I, Nr. 4, S. 275—293, 1914. 



Three fairly good wheat soils, one each from California, Kansas and Mary- 

 land were put down side by side in each of these three localities and cropped 

 with the same variety of wheat. The results indicated that the soil does not exert 

 the chief or preponderating influence in determining the phvsical properties or 

 the chemical constituents of the grain crop. Although no attempt was made to 

 trace out from these experiments the manner in which the climatic factors exert 

 the chief determining influence on the composition of the wheat crop, the follow- 

 ing possibilities are, however, considered: (l) Differences in humidity may cause 

 a difference in the transpiration of the plants, which in turn may react on the 

 composition of the crop. (2) Variations in the amount and distribution of sun- 

 light may influence diversely the photosynthesis of the plants. (3) Differences 

 in temperature and in the succession of hot and cold periods may cause varying 

 vegetative activities in the plants. (4) The climatic differences, such as the hu- 

 midity, rainfall, temperature, and sunlight, may bring about changes in the phv- 

 sical, chemical, or biological characteristics of the soil which in turn may react 

 on the crop. The climatic factors collectively have a strong determining influence, 

 especially upon the crude-protein content, the ash content, and the percentage 

 of phosphoric acid in the ash. 



The authors conclude that the results from this experiment harmonize with 

 the findings previously published namely, "that environment rather than what has 

 been usually termed heredity is the major i'actor in determining the physical and 

 chemical characteristics of the wheat crop. They indicate, further, that it is the 

 climatic environment which exercises the primary influence of the environmental 

 factors." Pearl. 



Geographische Verbreitung*, Reisen. 



1024) Orilinell, J., Barriers to distribution as regards Birds andMam- 

 mals. In: Amer. Naturalist, Bd. 48, Heft 4, S. 248—254, 1914. 



The opposing views of faunistic writers, that the distribution of animals is 

 controlled (l) chiefly by temperature or (2) by a composite series of ecological 

 factors, including previous distribution, is discussed with particular reference to 

 the birds and mammals of California and the western United States. The fol- 

 lowing Classification of barriers is made: 



A. Intangible. (a) Zonal (by temperature). (b) Fannal (by atmospheric 

 humidity). (c) Associational. (l) By food supply. (2) By breeding places. (3) By 

 temporary refuges. 



B. Tangible (mechanical). (a) Land to aquatic species. (b) Bodies or streams 

 of water to terrestrial species. 



The writer believes that the multiplication of species is brought about in 

 birds and mammals through the agency of barriers. Gates. 



1025) Chaiidler, A.C., The effect of extent of distribution on specia- 

 tion. In: Amer. Naturalist, Bd. 48, Heft 3, S. 129—160, 1914. 



The author considers the relation between the extent of distribution and the 

 amount of specific diversity in applicatiou to various groups of animals in dif- 

 ferent parts of the world. The term index of modification is used to indicate 

 the average number of species per genus. The bats and insectivora of the 



