234 
Journal of Agricultural Research 
Vol. XI, No. 5 
the soil. Molliard (1910) stated that the mycelium acted directly on 
the organic matter of the soil and produced ammoniacal salts which cause 
the stimulation of the grass the following season. 
Bayliss (1911) attributes the stimulation to the better nitrogenous 
nutrition due to the action of proteolytic enzyms on the dead roots. 
Munch (1914) stated that rings which produced no mushrooms showed 
the same stimulation and that the stimulation could therefore not be 
entirely due to decaying fruiting bodies. 
The mushrooms produced in eastern Colorado seldom decay in place. 
Marasmius oreades and even the species of Agaricus dry up in place and 
are often blown away. The spore masses of the puffballs are blown 
away, and the sterile bases remain in place for a year or more until loos¬ 
ened and blown away. Many of the fairy rings fruit only every few 
years, but are distinctly marked each year by the stimulated growth of 
the grasses and other plants. Although the fruiting bodies would stimu¬ 
late the growth of plants where they decay, the conditions in eastern 
Colorado are such as to minimize their effect. 
As already pointed out, the growth of the mycelium produces profound 
changes in the organic matter of the soil, liberating ammonia, which is 
again built up into nitrates or may form ammoniacal salts, both of which 
greatly stimulate the vegetation. The principal stimulation is probably 
due to these changes. Some indication of the effect of the decay of the 
mycelium on the stimulated growth may be obtained by a comparison 
of the rings formed by Agaricus tabularis and those formed by other 
fungi. In the case of A. tabularis the ring is very broad, the stimulated 
zone often extending back 2 to 5 meters or more behind the fruiting zone. 
In the Calvatia, Marasmius, or Catastoma rings, where only a small 
amount of mycelium is developed and where it is comparatively difficult 
to distinguish the threads in the soil, the stimulated zone is always narrow, 
seldom extending more than a meter behind the fruiting zone. In this 
case the stimulated area is the area in which the fungus filaments are re¬ 
ducing the organic matter of the soil while in the ring of Agaricus tabularis 
the larger inner stimulated zone is due largely to the decay of the mycelium. 
A comparison of the amount of ammonia and nitrates in the Calvatia and 
Agaricus ring shows that the ammonia is comparatively more abundant 
in the area occupied by the active mycelium and that nitrates are com¬ 
paratively more abundant in the area of dying mycelium. This sug¬ 
gests that the fungus mycelium reduces the protein of the organic matter 
rapidly to the end product ammonia but that during decay of the my¬ 
celium, which is accomplished by bacteria, and which probably takes 
place slowly, this end product is rapidly built up into nitrates. It 
would seem therefore that the greatest stimulation of vegetation would 
be found in the case of the fungus which had the greatest mass of my¬ 
celium. This is undoubtedly true, for in the case of Calvatia cyathiformis 9 
where only a small amount of mycelium is developed the stimulated 
