56 



CIRCULAR 14 3, U. S. DEPARTMENT OF AGRICULTURE 



The distinctive character of this genus is the steUate manner of 

 dehiscence, or breaking, of the two outer kxyers. The seiiinents 

 thus formed nuiy 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. 



GEASTEU HYGROMETBICUS. BAROMKTEll EARTH STAR 



In this species the periclium 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 pcridium is three-fourths to 1 inch in diameter. Tlie segments are 

 6 to 20 in number and are 2 to 3 inches in diameter when expanded. 



Gea-stcr hnyroinetriciis 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 

 ptrocess may occur repeatedly, depend- 

 ing on weatlier conditions, and hiisi 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 remarkal)le 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-shapecl body 

 knowm 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 (lireek words meaning 

 sac fungi. There are generally 8 

 spores or some midtiple of 8 — 

 though occasionally 4 — in an ascus. 

 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. 

 JNIorels, on the contrary, have a wider geographic distribution and 

 being terrestrial in.stead of subterranean like truffles are more con- 

 spicuous and bettei- known. 



Figure 48.- 



-Oea.ttcr radicaiis. 

 C. (J. LloytO 



(From 



