216 THE NORTH AMERICAN SLIME-MOULDS 



threads, the remains of peridium, extending from base to apex, where 

 the peridium remains intact, arcuate; hypothallus prominent, radiat- 

 ing far around the a^thalium, silvery white ; spores in mass, ochra- 

 ceous, or dull brownish yellow, by transmitted light almost colorless, 

 rough 9-10 fjL. 



Not rare, on decaying logs, especially of Tilia americana, where 

 in the same place successive fructifications follow each other some- 

 times for weeks together in the latter part of summer and early 

 fall. The jethalium is generally elliptical or elongate, 2-3 cm. in 

 extent, sometimes irregular or branched, varying in color according 

 to degree of maturity, weathering, etc. Plasmodium at first watery, 

 then pink, or flesh-colored. 



Eastern United States; common. Toronto; — Miss Carrie. 



E. CRIBRARIACEi^ 



Sporangia distinct, more or less closely gregarious, stipitate, the 

 peridium opening, especially above, by a well-defined network formed 

 from thickenings in the original sporangial wall. 



Key to the Genera of the Crihrariaceae 



A. Peridial thickenings in form of an apical net with definite thickenings 



at the intersections of the component threads . 1. Cribraria 



B. Peridial thickenings in form of parallel meridional ribs connected by 



delicate transverse threads 2. Dictydium 



Cribraria (Pers) Schroder. 



1794. Cribraria Persoon, Romer, A^. Bot. Mag., I., p. 91, in part. 

 1797. Cribraria Schrader, Nov. Gen. Plant., p. 1, in part. 

 1875. Cribraria Rostafinski, Mon., p. 229. 



Sporangia distinct, gregarious or closely crowded, globose or ob- 

 ovoid, stipitate ; the stipe of very varying length ; the peridium simple, 

 marked within by distinct and peculiar, granular, thickenings, which 

 below take the form of radiating ribs, supporting the persisting cup, 

 calyculus, and above, by extremely delicate anastomosing branches, 

 unite to weave a more or less regular net with open polygonal meshes ; 

 spores various, more often yellowish or ochraceous, sometimes brown, 

 reddish, or purple. 



