MUSHROOM GROWING. 45 



Table X. — Yields of experimental mushroom beds — Third series. 



In some publications on mushroom gjrowing the claim is made that 

 old or practically exhausted beds may be brought into bearing again 

 by heavy fertilization Avith liquid manure or with a weak solution of 

 potassium nitrate. From a commercial point of view, no measurable 

 success has resulted from any trials of this nature made by the writer ; 

 consequently, it is believed that exhausted beds should be immediately 

 discarded. From the standpoint of mushroom sanitation, this is 

 also particularly desirable. 



VARIABILITY IN 3IUSHR003IS GROAVN UNDER DIFFERENT CONDITIONS. 



The writer does not intend to discuss even in a general way the 

 relationships of the various forms of Agaricus — that is, those that 

 may be considered allies of A. ccmipeatr'Di — which he has cultivated or 

 studied in the field. Some reference to the variability of common 

 forms should, however, be made. For a comprehensive study of si)e- 

 cies and varieties, a knoAvledge of Furopean forms as well as of those 

 found in America is essential. Authors diU'er so widely in their 

 descriptions of species, as well as in their conce])tions of them, per- 

 haps, that in the absence of unlimited material nothing short of con- 

 fusion results from any attempt to harmonize opinions. It is suffi- 

 ciently difficult to separate what many would regard as varieties of 

 ^4, campestris from those of .4. arvensis. AMien specific rank is 

 bestowed also upon such forms as .1. pratenMs^ A. riUatinis, ^1. //uif/- 

 nifciis, A. rodmoni, etc., the difficulties are greatly increased. The 

 writer has grown many forms of Agaricus, and, as might be expected, 

 there seems to be no form which will remain practically constant 

 under variable conditions. Besides general size, size of spores, etc.. 



