lOO Forestry Quarterly. 



The first two mentioned are the poisonous substances and they 

 have been isolated from at least six strikingly sterile soils from 

 various parts of the United States. The first mentioned sub- 

 stance seems to be dependent upon the presence of fungi asso- 

 ciated with the roots of oak trees, in one instance at least. 



This Bulletin is very welcome, in that it apparently pushes 

 aside a little the veil that hides the causes of soil sterility. While 

 investigations like this are, for the present, applied to farm land, 

 they could be undoubtedly applied with very interesting results 

 to heaths, moors and other barren forest land. C. D. H. 



Distribution and Movements of Desert Plants. By Volney M. 

 Spalding. Carnegie Institution of Washington. Publication 

 No. 113. Pp. 144. 



The area studied by Professor Spalding occupies four square 

 miles including and adjacent to the Desert Laboratory domain at 

 Tucson, Arizona. The plant associations of the area are con- 

 sidered under nine principal groups as follows : The river 

 (Santa Cruz) and irrigating ditches; the river banks; the flood 

 plain; the salt spots; the wash (dry water course) ; the mesa-like 

 slopes; the hill (including various associations on different 

 aspects) ; the superficial soil layers associations and the asso- 

 ciations of parasitic and symbiotic plants. The characteristic 

 plants and the habitat factors of each association are described 

 and discussed. Then the author passes to a detailed considera- 

 tion of five characteristic species, showing by topographic maps 

 the exact location of each individual or groups of individuals and 

 discussing the factors of site which determine the location of each 

 species. For example, the creosote bush, the most abundant 

 plant, occupies as its principal habitat areas of course gravelly, 

 whitish transported (eroding) soils. The mesquite on the other 

 hand occupies areas of deposition (flood plains). In addition, 

 the most exclusive creosote bush areas are those where the layer 

 of caliche (lime-hard pan) comes most nearly to the surface, 

 while mesquite, as a rule, is absent from such areas. After 

 considerations like these, the author proceeds to discuss invasion, 

 competition and succession on the area. 



The discussions outlined above occupy the first two chapters 

 of the volume. The third chapter contains articles on climatic 



