232 
Journal of Agricultural Research 
Vol. XI, No. s 
In an oat field in 1915 a similar effect was noted but instead of a de¬ 
pressed growth over the dense mycelium area, the moisture supply had 
been sufficient to mature the crop on most of this zone. Along the line 
of fungus fruiting bodies the oat plants were small and weak. The 
relative height of the oat plants in different portions of the ring is given 
in Table XXIII. 
Table XXIII .—Height of oat plants in different zone of an Agaricus tabularis ring 
Akron , Colo., July 12, IQ15. 
Zone. 
Zone No. 
Height of 
plants. 
Inside. 
x 
Cm. 
77 
112 
60 
76 
Inner stimulated zone... 
2 
Fruiting zone... 
A 
Outside. 
*T 
5 
It is evident that in this case drouth was not operating to the detri¬ 
ment of the oat plants in such a wide portion of the area, and the usual 
depression of growth over the dead zone was not evident except in the 
immediate vicinity of the fungus fruits. The land had been plowed in 
the spring, and the heavy and continuous rains had maintained even the 
mycelium-impregnated soil in a moist condition. 
RINGS OR CAL/VATIA CYATHIFORMIS 
In figures 5 and 6 the principal zones found in rings formed by this 
fungus are sketched. The only effect produced on the vegetation by 
this fungus is to stimulate the growth on the area just inside the fruiting 
zone. The short grasses are not injured in these rings, and the weedy 
annuals do not enter. Festuca octoflora , Plantago purshii , Hedeoma 
hispida , and the short grasses usually grow luxuriantly in this stimulated 
zone. Their growth is more rapid, and the plants darker green in color. 
The stimulated zone in these rings does not differ essentially as to vege¬ 
tation from the outer stimulated zone of the ring of Agaricus tabularis; 
and since the perennial vegetation is not killed, the bare zone does not 
exist, nor is the inner stimulated zone (or weed zone) of the Agaricus 
ring represented in the Calvatia ring. The position of the stimulated zone 
in Calvatia rings is within the circle of fruits instead of outside of it, as in 
the case of the outer stimulated zone 4 in Agaricus rings. 
The vegetation inside does not differ from that outside, excepting fol¬ 
lowing years of more than normal moisture supply, when the short grass 
cover just inside becomes more dense than outside, due to better growth 
in the stimulated zone (PI. 27, B). 
The effect of Calvatia cyathiformis on the cultivated crop is similar 
to that on the native. During dry years, such as 1916, no effect could be 
noted. It is evident from the remapping (fig. 8) of the area shown in 
