CHARACTERISTICS OF AGARICUS 



expanded part known as the cap or pileus. 

 The latter is in reality a very essential part, 

 producing, as noted later, the spores, or 

 propagative structures. The diameter and 

 thickness of the pileus vary considerably in 

 the different varieties, and with the condi- 

 tions of the environment under which the 

 plant is grown; but usually the diameter of 

 the cap is about equal to the height of the 

 stalk, and the thickness of the cap is about 

 equal to the diameter of the stalk. The 

 upper surface of the cap gives the main 

 color tone to the plant, and this, too, varies 

 in the different varieties from almost pure 

 white or cream to purplish gray or dark 

 brown. 



The stem is usually cream or white and 

 near the upper or cap end it is encircled by 

 a ring or collar of tissue, known as the an- 

 nulus. The annulus is the remnant of that 

 tissue which in the younger plants connects 

 the stem with the periphery of the cap, thus 

 forming a covering over the delicate struc- 

 tures on the under surface of the cap. The 



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