DiCTYDIAETHALIUM 215 



Family IV. RETICULARIACEAE 



Sporangia closely compacted and usually forming an aetha- 

 lium; sporangial walls without plasmodic granules, usually incom- 

 plete, perforated, or forming a spurious capillitium; true capilli- 

 tium none, or in Liceopsis consisting of a few branching threads 

 and strands. 



Fructification always in aethalia. 



Component sporangia columnar; sporangial walls 

 incomplete, dome-shaped at the apex, contin- 

 ued toward the base in four to six straight 



threads. ii. Dictydiaethalium 



Walls of the convolute, component sporangia 

 perforated and forming a uniform tissue of 

 interarching bands. 34. Enteridium 



Walls of component sporangia incomplete and 

 indefinite, forming plates and strands with 

 numerous long threads. 35. Reticularia 



Fructification usually of closely compacted, sub- 

 globose sporangia, sometimes forming aethalia; 

 inner walls usually complete. 36. Liceopsis 



Genus Z3. DICTYDIAETHALIUM Rostafinski, Versuch 5. 

 1873. 



Aethalium pulvinate, formed of erect, columnar sporangia; 

 sporangial walls incomplete, dome-shaped at the apex, continued 

 to the basal membrane in four to six straight threads; capillitium 

 none. 



A SINGLE SPECIES. 



1. Dictydiaethalium plumbeum (Schum.) Rost. Versuch 5. 1873. 

 Fuligo plumbea Schum. Enum. PI. Saell. 2: 193. 1803, 



Plasmodium rose-red (Lister). Aethalium pulvinate, smooth, 

 flattened, 1 to 10 cm. across, 0.5 to 1 mm. thick, olivaceous or 

 ochraceous, areolated with the convex apices of the sporangia, 

 usually surrounded by a white, membranous hypothallus; sporan- 

 gia cylindrical, angled by mutual pressure, 0.5 to 1 mm. high, 0.2 

 mm. broad ; sporangial wall ochraceous or yellow, persistent, and 

 forming a flat or dome-shaped cap at the apex, sometimes dark 

 with superficial deposits of refuse matter, continued down to the 

 basal membrane in four to six straight threads, evanescent be- 

 tween the threads. Spores ochraceous or yellow in mass, pale 



