MUSHROOMS AND OTHER COMMON FUNGI. • 51 



portion which has attained the surface remains, covering the inner 

 peridium like a cap or inverted cup; consequently, the apparent apex 

 at which the mouth is situated is the actual base of the plant as it 

 grows. The capillitium threads are similar to the densely interwoven 

 hyphae, which form the inner peridium and are evidently branches 

 of them radiating from the interior." ' (Morgan, vol. 14, P- H2.) 



Catastoma circumscissum. 



Peridium subglobose, more or less depressed, and often quite irregular; cortex thick- 

 ish, fragile, usually rough and uneven from the adhering soil, after maturity torn away, 

 leaving the lower two-thirds or more in the ground ; inner peridium depressed-globose, 

 subcoriaeeous, rather thin, pallid, becoming gray, minutely furfuraceous, with a small 

 regular basal mouth. Mass of spores and capillitium soft, compact, then friable, oliva- 

 ceous, changing to pale brown (fig. 1; from Morgan). 



GEASTER (EARTH STARS). 



In the genus Geaster the peridium consists of three persistent coats. 

 The two outer coats generally adhere and form the thick, fleshy- 

 coriaceous exoperidium, 

 which at maturity splits from 

 the apex into several seg- 

 ments; the inner coat, the 

 endoperidium, is more or less 

 parchmentlike, either sessile 

 or short stalked, and opens by 



, Fig. I.— Catastoma circumscissum, showing method of 



an apiCa L mOUth. 1 he Spores growth, early and late stages. The cross section (at top) 

 are USUlllv dark brown and shows the origin of the threads of the capillitium. (After 



mixed with capillitium. 



The distinctive character of this genus is the stellate manner of 

 dehiscence of the two outer layers. The segments thus formed vary 

 from spreading, inrolled, or recurved to arched. The accompanying 

 illustration (PI. XXXVI, fig. 1 ) 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 elevation of the endoperidium. 



Geaster hygrometricus. 



Peridium depressed globose; exoperidium splitting at the apex divides into a varia- 

 ble number of strongly hygrometric segments, which are rigidly inrolled when dry and 

 expanded when moist; endoperidium whitish gray or brown, thin, membranaceous, 

 with a small, irregular mouth. 



Inner peridium three-fourths to 1 inch in diameter. Segments 6 to 20 in number, 

 2 to 3 inches in diameter when expanded. 



Geaster hygrometricus is the species most frequently collected. It is common in 

 woods, sandy locations, or partially cleared land. The peculiarity of this species is 

 the hygroscopic nature of the exoperidium. In dry weather the segments are strongly 

 recurved, but in wet weather they expand. This process may occur repeatedly, 

 depending on weather conditions, and it is often called the " poor man's weather glass." 



