4 
Mycologia 
iginosa are annual. Growth may go on at the margin until well 
into the autumn and as a result an increase in surface area occurs, 
but in no case was a new hymenial formation found the following 
spring. After the first season, the hymenial surface loses its 
rich rubiginous color and becomes dull and grayish-brown. As 
the fungus dries out, as happens in many cases, extensive checking 
occurs. The fruit bodies of the season are readily discernable 
from those of former years because of the differences enumer- 
ated above. 
The fungus is essentially a xerophyte. It withstands to a re- 
markable degree the many vicissitudes of climate and recovers 
well after a prolonged drought. Within a few hours after pre- 
cipitation, spore formation begins again and continues as long 
as favorable conditions prevail. Interrupted spore formation 
may go on in this way during the summer and autumn. 
The time at which fruit bodies first begin to shed spores varies 
with conditions. Fruit bodies with a surface area of a square 
centimeter were found to be producing viable spores, and it is 
possible that spore formation may have begun when they were 
much smaller. Spore formation begins before the fruit bodies 
have attained their ultimate size and continues with many inter- 
ruptions until late autumn. 
Structure of the Fruit Bodies . — There are three distinct layers 
discernable (Fig. i8), which give to the fruit body a stratose 
structure. The lower exposed layer bears the hymenium on its 
outer surface and makes up the greater part of the thickness of 
the fruit body (Fig. 4) and its limits of variation are sueh that a 
fruit body may be fully twice as thick in some places as in others. 
The second layer consists of a narrow stratum of hyphae near 
the upper surface, closely entwined and fastened together. The 
third and last is a loose, floccose stratum of hyphae, in which the 
course of the filaments as individuals may be readily followed. 
The last two layers exhibit little variation in thickness. 
The hymenium of the species under consideration (Fig. 19) 
consists of three distinct structures, viz. : large and prominent 
brown cystidia (a), colorless basidia {h), and a third element 
similar to the basidia, but shorter and only slightly enlarged at 
the tip (c). These may be immature basidia which subsequently 
