CIRCULAR 14 3, U. S. DEPARTMENT OF AGRICULTURE 



FiGCBE 1. — A, A gill-l3earing mushroom : c, 

 Pileus or cap ; b, gills ; c, stem ; d, ring ; 

 e, volva or cup. B. A tube-bearing or 

 pore-bearing mushroom (section of uppor 

 I)art) : a, Cap ; b, tubes or pores ; c, view 

 of part of lower side of cap 



AGARICACEAE (GILL FUNGI) 



Plants of the family Agaricaceae (gill fungi) have 'a well-defined 

 stem or stipe, which bears an expanded portion known as the cap or 

 pileus. On the lower surface of the cap are platelike structures 

 known as gills or lamellae, on which the spores are borne, (Fig. 1.) 



The manner in which the gills 

 are attached to the stem is of 

 great importance in determining 

 species and should be carefullj^ 

 noted in the field. The best 

 method of determining the man- 

 ner of attachment is to cut the 

 mushroom longitudinally 

 through the cap, thus exposing 

 the point of attachment of the 

 gills and stem. The terms de- 

 scriptive of this attachment may 

 be best understood by referring 

 to Figure 2. 



If the mature mushroom is 

 shaken, a fine powder may be seen falling from the gills. This 

 powder consists of thousands of spores, which, through the agency of 

 the wind, birds, or insects, are widely distributed. The color of the 

 gills is a very important character in the determination of mush- 

 rooms and depends upon the color of the spores, which may be white, 

 cream, yellowish, rose, brown, black, or purplish. The color may be 



conveniently deter- 



termined by making 

 a spore print as fol- 

 lows: 



Cut the stem off 

 close to the cap and 

 place the cap, gill 

 side down, on a piece 

 of paper. Ordinary 

 white paper will 

 serve the purpose 

 unless the mushroom 

 has white or light- 

 colored spores, in 

 which case a colored 

 paper will be more 

 satisfactorv. Spores 

 so collected consti- 

 tute a spore print and may be made permanent by spraying them 

 with a solution of white shellac in alcohol. A saturated solution 

 should be made and then diluted to 50 per cent with alcohol. 



The stem is often an important diagnostic character; therefore 

 careful descriptive field notes should be made of its color, size, shape, 

 and texture. 



In the early stages of development of certain genera and species the 

 gills are covered with a membrane known as the veil, extending from 

 the margin of the pileus to the stem. This veil may entirely dis- 



FiGURB 2. — Mushrooms showing varying shapes of caps, and 

 kinds of gills : A, Cap umbonate, gills free ; B, cap con- 

 vex ; C, cap funnelforni, gills decurrent ; D, cap expanded ; 

 E. gills emargiuate 



