56 CIRCULAR 143, U. S. DEPARTMENT OF AGRICULTURE 
The distinctive character of this genus is the stellate manner of 
dehiscence, or breaking, of the two outer layers. The segments 
thus formed may be spreading, inrolled, incurved, or arched. 
Figure 48 shows a form of the latter type in which the two layers 
of the exoperidium separate, the outer remaining as a segmented 
basal cup while the inner layer becomes arched and causes the ele- 
vation of the endoperidium. 
GEASTER HYGROMETRICUS. BAROMETER EARTH STAR 
In this species the peridium is depressed globose; the exoperidium splitting 
at the apex divides into a variable number of strongly hygroscopic segments, 
which are rigidly inrolled when dry and expanded when moist ; the endoperidium 
is whitish gray or brown, thin, membranaceous, with a small irregular mouth. 
The inner peridium is three-fourths to 1 inch in diameter. The segments are 
6 to 20 in number and are 2 to 8 inches in diameter when expanded. 
Geaster hygrometricus is the species 
most frequently collected. It is common 
in woods, sandy locations, or partly 
cleared land. The peculiarity of this 
species is the hygroscopic nature of the 
exoperidium, the segments of which 
in dry weather are strongly recurved 
and in wet weather expand. This 
process May occur repeatedly, depend- 
ing on weather conditions, and has given 
rise to the common name for this 
species, the poor man’s weatherglass.” 
ASCOMYCETES (SAC FUNGI) 
The group of fungi known as 
Ascomycetes comprise a very large 
number of species remarkable for 
great variation in form, structure, 
color, size, and habit. In the spe- 
cies considered so far the spores 
have been borne externally on a 
more or less club-shaped body 
known as the basidium, generally 
four spores to a basidium. In the 
Ascomycetes the spores are pro- 
duced in very small sacs or asci, 
the term Ascomycete being derived 
from two Greek words meaning 
sac fungi. There are generally 8 
spores or some multiple of 8— 
Mieune 45-— Geaster radrcans.” (Brom though occasionally 4 in, anacene. 
ct The spores are very minute, and 
without the aid of a microscope they appear as a fine powder. 
Many of the species of Ascomycetes are highly parasitic and 
cause many serious diseases of agricultural crops, while a few are 
edible and highly regarded as articles of food, as, for example, 
_ truffles and morels. While certain species of truffles are to be found 
in the United States, they are not very common or well known. 
Morels, on the contrary, have a wider geographic distribution and 
being terrestrial instead of subterranean like truffles are more con- 
spicuous and better known. 
