412 IOWA ACADEMY OF SCIENCE 



ance to those of the Nidularacese. This character is subject to a 

 very wide range of variation so that in some eases it is necessary 

 to rely entirely on the peridium to determine to which genus a 

 given specimen should be referred. 



KEY TO THE SPECIES. 



Distinct peridioles absent at maturity; periderm rather persistent. 

 Periderm rupturing irregularly. 

 Periderm thick. 



Periderm conspicuously warty or scaly 



1. Scleroderma aurantium 



Periderm smooth, or smoothish 2. Scleroderma Caepa 



Periderm thin. 



Periderm rather firm and flexible, smooth or scaly 



3. Scleroderma Bovista 



Periderm fragile above, warty 4. Scleroderma verrucosum- 



Periderm rupturing stellately. 



Spore-mass light colored 5. Sclerangium flavidum 



Spore-mass appearing almost black 6. Sclerangium polyrhizon 



Distinct peridioles present at maturity; periderm very fragile 



7. Pisolithus arenarius 



I. SCLERODERMA Persoon. 



Sporophore subglobose, with rhizomorphs and frequently 

 rhizoids, or even a stalklike base ; peridium single, usually thick, 

 rather firm, opening irregularly; gleba homogeneous, capillitium 

 none, the boundaries of the spore cavities remaining as more or 

 less distinct lines of hyphas; spores globose, roughened. 



1. SCLERODERMA AURANTIUM (L.) Pers. (S. vulgare Hornem.) 



Subglobose, subsessile, radicate or not, 2.5 — 8 cm. in diameter ; 

 periderm thick, corky, usually pale with shades of yellow or 

 orange, or sometimes brownish, usually covered with large warts 

 which are more or less deciduous; gleba at first white, changing 

 through various shades to blue-black and finally greenish gray; 

 lines of trama yellowish ; spores dark, globose, warted, 7 — 12 f 1 in 

 diameter. 



Johnson county (Macbride, Shimek, Miss Jewett), Linn county 

 (Shimek), Muscatine county (Shimek). 



The commonest species in our territory and one of the largest. 

 It presents a considerable variation in the size and pattern of the 

 warts on the periderm. The specific name is frequently incor- 

 rectly written "aurantiacum." 



