The Myxomycetes of Eastern Iowa. 113 



KEY TO THE FAMILIES OF THE MYXOGASTERES. 



I. Spores not included in sporangia, Ceratiomyxace^. 



{Exospoi-ecc, Rostafinski.) 



II. Spores included in sporangia. 



{Endosj>orece, Rostafinski.) 



A. Capillitium wanting. 



1. Peridium simple, breaking irregulai-lv, . . Liceace^. 



2. Sporangia uniting to form sethalia, inter-communicating 



laterally, or on all sides, . . . Clathroptychiace^. 



3. Sporangia single with net-like thickenings, CRiBRARiACEiE. 



B. Capillitium present. 



1. Fruit free from deposits of lime. 



a. Columella none; threads of capillitium tubular, 



Trichiace^. 



b. Columella prominent (usually); capillitium not tub- 



ular; spores violet-tinted. 



* Sporangia in a^thalia; spores brown, 



Reticulariace^. 



* * Sporangia distinct; spores violet tinted, 



Stemoxitac.e. 



2. Fruit with calcareous deposits. 



a. Capillitium with lime crystals or free from calcareous 



deposit. 



* Capillitium without lime; columella present, 



SPUMARIACE.t;. 



* * Capillitium with crystals, if lime be present, 

 no columella, . . . Didymiace^. 



b. Capillitium containing lime in amorphous grains, 



Physarace^. 



I. CERATIOMYXACE/E. 



Sporangia none. Spores superficial, borne on erect papilla?, 

 or even on the walls of minute depressions or pits ; each spore 

 surmounting a delicate pedicel or stalk. The spores on 

 germinating give rise to amoeboid zoospores which undergo 

 repeated divisions, later become ciliate, and at length again 

 amoeboid to blend into genuine plasmodia. At maturity the 

 Plasmodium gives rise to numerous minute divisions, each of 

 which may lengthen in a direction perpendicular to the surface 

 and bear a spore at the tip. 



