BOOKS AND CURRENT LITERATURE 271 



Of the systematic investigations of individual genera that have been 

 begun the author's report is very brief, but enough is presented to indi- 

 cate substantial progress, in the course of which the story of ancestral 

 forms and the derivation and migrations of species that have arisen from 

 them since early Tertiary times is, at least in part, being unravelled. 



V. M. S. 



Soil Fungi. — This paper 1 is the result of a recent investigation on 

 the fungi in arable soils. It consists, in the main, of a monograph of 

 the forms, some of which are new to science, which the author obtained 

 by a method of isolation somewhat different from any that has hitherto 

 been employed in work with soil fungi. This method is carefully de- 

 scribed in the paper. Nearly all the forms were found to be obligate 

 saprophytes. As is pointed out, however, failure to isolate certain forms 

 may be due to a lack of suitable media and other environmental factors. 

 Emphasis is laid on the fact that in plant pathological work the applica- 

 tion of rational methods of control necessitates, first of all, not merely 

 circumstantial evidence relative to the organism involved but a com- 

 plete knowledge of its life cycle. It is, of course, generally recognized 

 that even though certain forms are known to hibernate in decaying plant 

 tissues, yet one might not be able to isolate them because they do not 

 grow in culture or only so slowly as to be overrun and their growth thus 

 inhibited. Those who have done any considerable amount of culture 

 work realize that certain facultative parasites seem to have a dormant 

 period during which time growth on media cannot be induced, and that 

 others can be cultured only on sterilized portions of the host or in an 

 extract from it. — Frederick A. Wolf. 







1 Jensen, C. N., Fungous Flora of the Soil. Cornell Agr. Exp. Sta. Bull. 315: 

 415-501, figs. 100-134. 1912. 



