The Fly-Agaric (Agaricus muscarius), though in general structure it closely resembles the common mushroom (Ag. campestris), is to be avoided as a poisonous species. Large orange or crimson cap, more or less thickly dotted with whitish flakes. Underside of the cap (pilcus) will has thin yellowish plates set on edge and radiating from the stem to the circumference. Over these plates or gills is stretched a membrane, called the hymenium, on which the spores are borne.