growth. This arrangement is not as rigidly exact as would be 
desirable, but it throws those species together that are most 
closely related to each other, and is therefore natural. 
The essential characters to be noted in all the species in this 
genus are, gills free from the stem, pink colored before maturity, 
blackish-brown or black when fully mature, spores brown, and a 
stem bearing a ring or collar. There are many similar mush- 
rooms which are not known to be edible but which have pink 
gills. Their gills, however, never become brown or blackish- 
brown; their spores are pink, and their stem never has a collar. 
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