408 VEGETABLE FORCING 
Fig. 147.—Wooden mushroom houses at Kennett Square, Pa. 
Botanical characteristics—The cultivated mushroom 
so familiar to growers in the United States is botanically 
known as Agaricus campestris. It consists of a stalk or 
stipe, varying in height from 2 to 5 inches, and in 
diameter from ™% inch to 1 inch. The top or expanded 
part of the mushroom is known as the “cap” or “pileus”’; 
this varies greatly in thickness and diameter, according 
to variety, stage of growth and condition under which it 
is grown. Varietal variations are rather marked, the caps 
of some being whitish, while others are creamy white or 
perhaps brown. The leaflike or gill-like projections on 
the under side of the cap are termed gills or “lamelle”’ ; 
these, for a time, are pink in color in the white or cream- 
colored species, but they subsequently turn brown or 
brownish black. The dark-colored spores are borne on 
the gills, and they serve as the reproductive bodies of the 
mushroom. 
Spores are the normal propagative bodies of this fungus, 
but growers do not use them directly in the production of 
mushrooms, although under favorable conditions they 
will germinate and ultimately produce a_threadlike 
growth termed the “mycelium.” 
Where to grow mushrooms.—The most extensive 
mushroom plantations in the world are in France. The 
city of Paris, built of stones largely taken from quarries 
