AGARICS WITH BLACK SPORES 



conditions; so that the differences between 

 specimens produced under both favorable 

 and unfavorable conditions might be con- 

 trasted. At the present time the writer has 

 in cultivation some ten or twelve forms 

 which appear to be more or less distinct. 

 Some of these, however, belong to spe- 

 cies other than the two above referred 

 to. We commonly understand that the 

 typical form of A. campestris possesses 

 gills which are at first bright pink, chang- 

 ing to bright reddish brown, and finally 

 to brown-black; that the annulus is sin- 

 gle and relatively not much thickened 

 as a rule; that the cap is convex or 

 plain, varying from white to brownish; 

 and that the stem is equal and solid. It 

 has been found, however, that under the 

 conditions of vigorous production in cel- 

 lars or mushroom houses spawn derived 

 from the typical field species may yield 

 specimens in which the color and ring 

 characteristics are not distinguishable from 

 those commonly identified as A. arvensis. 



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