4 CIRCULAR 143, U. S. DEPARTMENT OF AGRICULTURE 
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 carefully 
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 
Figure 1.—A, A gill-bearing mushroom: a, gills and stem. The terms de- 
futons 0 CAD Oe SUS Ee eae ee /ecripulve of this attachment may 
pore-bearing mushroom (section of upper be best understood by referring 
part) ia, Cap 0, tubes oF pores, VieW to Wionre 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 A 
close to the cap and ) 
place the cap, gill £ 
side down, on a piece 
of paper. Ordinary 
| 22 
white paper will 
serve the purpose 
unless the mushroom 
has white or lght- 
C Pe 
colored spores, in 
which case a colored 
= = Ficurp 2.—Mushrooms showing varying shapes of caps and 
paper will be | more kinds of gills: A, Cap umbonate, gills free; B, cap con- 
satisfactory. Spores vex: C, cap funnelform, gills decurrent ; D, cap expanded ; 
: E, gills emarginate 
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 
caziul 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- 
