Orcadella. 49 



I am indebted to the kindness of the author for an oppor- 

 tunity of examining authentic specimens, and quite agree as 

 to the validity of the generic characters, and also admit that 

 the new family founded is quite as good as most others at 

 present admitted in the Myxomycdes, but I am afraid that if 

 such trivial characters are admitted as sufficient for family 

 characteristics, those left for generic distinctions will be reduced 

 to inappreciable quantities. 



Compared with allied genera, as Claihroptycliium and 

 Enteridium, we find that in the genus under consideration, the 

 apical portion of the sporangium is differentiated and event- 

 ually disappears, whereas in the two last-named genera the 

 differentiation and disappearance of the sporangium is confined 

 to certain portions of the lateral wall ; or finally, it may be 

 looked upon as a scattered, stipitate Tiibulina with a dehiscent 

 apex to the sporangium. 



Distrib. United States: species 1. 



Orcadella operculata, Wing. (f. 201). 



Sporangia stipitate, without columella or capillitium, very 

 variable in form, barrel-shaped, urn-shaped, vase-shaped, jar- 

 shaped, ovoid or nearly globose, or all varieties appearing in 

 one small group ; stipe slightly tapering, erect or bent, blackish, 

 rough and coarse from deposits of plasmodic refuse; very 

 variable in height. Sporangium wall likewise coarse, blackish, 

 containing deposits of plasmodic refuse, but at the top part 

 of the sporangium replaced by a delicate, yellowish, iridescent, 

 lustrous or vernicose membrane which forms a flat or slightly 

 convex circular deciduous lid, sometimes smooth, sometimes 

 reticulately wrinkled. Mass of spores yellowish. Individual 

 spores almost colourless, globose or irregularly roundish, smooth, 

 8 11 n in diameter. 



Orcadella operculata, Wing., Proc. Acad. Nat. Sci. Phil, 1889, 

 p. 280, with fig. 



(Type in Herb. Acad. Nat. Sci. Philada.) 



On trunks of living red-oak trees (Ouercus ruber). United 

 States. 



