202 
Journal of Agricultural Research 
Vo]. XI, No, s 
in the surrounding sod. If the season is favorable and a second crop of 
puffballs is produced, they appear outside in advance of the stimulated 
zone (PI. 26, A). 
RINGS FORMED BY CAEVATIA POLYGONIA 
The giant Calvatia polygonia Lloyd is somewhat less abundant on 
the Great Plains than the one just discussed. It occurs frequently 
in eastern Colorado, and forms large rings not differing essentially from 
those described for 
Calvatia cyathiformis. 
The rings formed by 
this fungus are usually 
intermediate in size, 
one ring having been 
noted with a diameter 
of ioo meters (PL 
28, B). 
RINGS FORMED BY CATAS- 
TOMA SUBTERRANEUM 
The interesting fun¬ 
gus Catastoma subter - 
raneum (Pk.) Morg., 
the fruiting bodies of 
which develop under¬ 
ground and do not 
appear on the surface 
until after they have 
broken loose from their 
attachment, forms no¬ 
ticeable rings indicated 
by a stimulation of 
the native plant cover. 
The rings thus far 
noted by the writers 
have not been complete (PL 30, B). Fruiting bodies are formed near the 
convex side of the stimulated area. The effect on the native vegeta¬ 
tion is the same as in the case of Calvatia cyathiformis , but the stimulated 
zone is even narrower. 
• /7/RSrcy^Q^ 
Fig. 5.—Sketch of a ring produced by Calvatia cyathiformis. The stim¬ 
ulated zone is most marked at the outer edge just inside the ring of 
fresh puffballs. If a second crop of puffballs are produced, they occur 
at the points marked °. In this ring there is a stimulated zone (2) 
lying between the normal vegetation inside (1) and the fruiting zone, 
which occurs at the inner edge of the normal vegetation outside (3). 
RINGS FORMED BY OTHER FUNGI 
Lycoperdon gemmatum and L. wrightii , which occur more commonly 
on cultivated and disturbed land, indicate little effect in stimulating the 
vegetation. Calvatia fragilis Vitt, Marasmius oreades (Fr.) Bolt, Agaricus 
campestris L. (PL 28, A), and Tricholoma melaleuca (Pers.) Quel, occur 
