AGARICS WITH BLACK SPORES 



resent several species. Among the species 

 common in the United States botanists have 

 distinguished, of course, ''typical" Agaricus 

 campestris, the Field Mushroom, from A. 

 arvensis, the Horse Mushroom. Undoubt- 

 edly characteristic forms of both these spe- 

 cies are w^idely cultivated. Intergrading 

 forms or varieties also occur, and it is often 

 very difficult to determine v^hether these 

 may be more properly regarded as varieties 

 of the two species mentioned or as consti- 

 tuting forms perhaps closely related, but to 

 which others would assign specific rank. 

 Some botanists would assign specific rank, 

 for example, to such forms as A, magnificus 

 and A. Rodmani among others. 



In Europe A. pratensis [A. praticola) 

 and A. villaticus are among those recog- 

 nized as related species. Types correspond- 

 ing to these last mentioned also occur in the 

 United States. Referring, in an earlier 

 publication, to the forms of Agaricus in cul- 

 tivation, it was suggested that in the absence 

 of any possibility that the grower would 



147 



