Oct. 29,1917 
Fungus Fairy Rings 
213 
EFFECT OF WEATHER CONDITIONS ON THE CHARACTER OF THE 
FRUITING BODIES. 
The effect of high temperature on the fruiting bodies is well known. 
Fruiting bodies which appear during damp, warm periods decay rapidly 
and are soon destroyed by maggots. On the other hand, those which 
appear during cool periods remain fresh for a much longer time. 
On the Great Plains it often happens that a spell of wet weather will 
be followed by an exceedingly dry period in which the evaporation from 
the soil and transpiration from the plant surface is excessive. When 
the fruiting bodies of the fungus are produced during such a dry period, 
the shape and proportions of these bodies and the character of the top of 
the pileus are greatly modified. The fruiting bodies of Agaricus tabu- 
laris produced during a period of rapid evaporation have a very rough 
and scaly periderm, a thick, firm pileus, and a short, thick stipe. These 
present better herbarium material when dried in place than when dried 
in a drying oven. On the other hand, if the fruiting bodies are produced 
during a period of less excessive evaporation, the pileus is thinner and 
expanded, the stipe long, and the periderm often quite smooth. These 
decay rapidly, and are difficult to preserve. In 1909 the tops were 
mostly rough (PI. 10, B, C). They were produced during a period of 
comparatively rapid evaporation. During the year 1915 the tops were 
either smooth or rough, depending upon the time of appearance and 
the exposure. The fruiting bodies produced among taller growing 
plants and grasses almost invariably had smooth tops (PI. 11, A), while 
those which occurred in the open had rough tops (PI. 11, B, C). 
The Agaricus tabularis ring sketched in figure 10 was partly in a corn¬ 
field and partly in the open. The fruiting bodies developed in the corn¬ 
field were comparatively smooth on top, the pileus spread out very wide 
and thin, and the stipe comparatively long and slender, while the fruits 
produced in the short-grass sod had a thick, firm, pileus, rough on top, and 
a very short and stocky stipe. The differences were similar to those 
shown in Plates 11 and 12. 
The amount of variation in the pileus is well illustrated by the fresh 
sporophores shown in Plates 10 and 11 and the dried sporophores 
shown in Plate 12. In Plate 12, A and B, the characteristic pileus of 
Agaricus tabularis is shown, while in Plate 12, C and D, this tabular 
structure is entirely lacking. 
Duggar (1905), who has made an extensive study of wild and cultivated 
forms of Agaricus, calls attention to the great amount of variation pro¬ 
duced in the different strains under different cultural conditions. This 
wide range of variation and the effect on morphology, color, etc., make 
doubtful the specific value of forms showing only slight morphological 
differences (Duggar, 1915). 
