46 MUSHROOM GROWING AND SPAWN MAKING. 



some of the characters used in separating the common forms are color 

 of gills ; character of ring, particularly as to whether single or double ; 

 shape of stipe; color and markings of pileus; color of flesh, etc. In 

 following the develoi)meiit of these characters in different forms, 

 many variations Avill be found. Ar/apicus campestris grown on com- 

 posted leaves shows very little pink in the gills. The color changes 

 rapidly from dull pinkish-brown, or almost white, to a leaden hue. 

 Several brown-capped forms, usually considered varieties of A. cam- 

 pestris^ ^never show a bright-pink surface unless produced under 

 exceptionally^ favorable conditions, moist air being a sine qua non. 

 The ring is naturally variable. In any variety of ^1. campestris it is 

 not uncommon for an edge of the partial veil to remain attached to 

 the base of the stem as a volvate line, or this line may be left at any 

 stage during the elongation of the stem. Again, if the lower margin 

 of the partial veil on the stipe separates slightly from the stipe, and 

 upon drying curves slightly upAvard, there is an indication of a double 

 ring. A very good double ring appeared on a number of very vig- 

 orous specimens of an undoubted variety of A. campestris during the 

 present season. It is possible that there is a greater tendency to pro- 

 duce a double ring when conditions are favorable for the production 

 of the most vigorous mushrooms. Agaricus arvensis is also very 

 variable with respect to the formation of a double ring, as also in the 

 persistence of the partial veil. 



The shape of the stipe is in many forms dependent upon the con- 

 ditions. Under favorable conditions a brown variety of .1. cam- 

 pestris may have a very short, thickened, equal stem, when grown on 

 manure, and practically uniform at maturity, while the same form 

 groAvn on decayed leaves may show in the main a stipe Avith thicks 

 ened base, gradually tapering to the top. The color of the cap is of 

 undoubted value as a varietal or specific character, yet it must be 

 remembered that whether the surface be smooth or rough, merely 

 fibrillose, or broken into scales of definite form, may depend entirely 

 upon Avhether produced in moist air or in dry air, subjected to 

 drying after being Avet, etc. The color of the flesh is also dependent, 

 to a considerable extent, upon the conditions. A specimen groAvn in 

 even fairly unfavorable conditions Avill sIioav the flesh someAvhat 

 darkened, and on exposure the characteristic pink tint will not be 

 even momentarily visible. In other Avords, a considerable range of 

 A^ariation nuist be anticipated, and in comparisons there should be 

 stated very cknirly the conditions under Avhich the particular forms 

 are produced. 



THK CL JVnVATION Ol' VARIOUS SPECIES OF MUSHUOOMS. 



In Table X are given the results of a single test Avith 'Agaricus 

 (u-rcHsis, or Avhat is supposedly a broAvn variety of this species, and 



