PAPEKS ON BOTANY 



125 



8. The data also support the theory that many of the 

 black-soil prairies of Illinois originated from glacial lakes 

 and swamps and have existed as prairies since glacial times. 



The work is still under way and it is hoped that a detailed 

 report will appear in 1917. The final report will be pub- 

 lished as a Bulletin of the State Natural History Survey. 



SOME INTERESTING MUSHROOMS OF CHAM- 

 PAIGN COUNTY 

 W. B. McDougall, University of Illinois 



Among the mushrooms collected in the vicinity of Urbana, 

 Illinois, during the past two years there are three to which 

 especial interest attaches, for a different reason in each case. 

 The first of these is Russula foetentula Pk. (Fig. 1). This 

 species is easily recognized by its reddish yellow, viscid pileus 

 which is conspicuously striate at the margin, and from its 

 odor, which is that of bitter almonds. Other distinguishing 

 features are the pale yellow color of the spores and reddish 

 brown stains at the base of the stem. R. foetentula was de- 

 scribed from New York by Peck in 1906 and seems not to 

 have been found commonly elsewhere. This may be due to 

 the fact that it is rather easily mistaken for R. foetens Fr., 

 to which it is closely related. It is a very distinct species, 

 however, differing from R. foetens in having the odor much 

 less pronounced, in the closer gills and in the reddish stain 

 at the base of the stem, as well as in the color of the spores 

 which in R. foetens are white. 



The interesting thing about this mushroom is that it habit- 

 ually produces mycorrhizas on the white oak (Ouercus alba) 

 trees in the "forestry," an artificial woodlot at the University 

 of Illinois. R. foetentula has not previously been reported as 

 a mycorrhiza former. In fact, only one species of this very 

 large genus, and that an undescribed species, has been so re- 

 ported. 1 R. foetentula occurs quite abundantly during favor- 

 able weather among the white oaks of the forestry, from the 



