280 PROCEEDINGS OF THE ACADEMY OF [1889. 



ORCADELLA OPERCULATA Wing., A NEW MYXOMYCETE. 

 BY HAROLD WINGATE. 



This curious minute plant presents anatomical characteristics 

 which lead me to propose a new family of the Myxomycetes, and 

 which, in Dr. Rostafinski's classification, would come under Order IV, 

 Anemeae, and after Family 13, Glathroptychiaceae. 

 ORCADELLACEAE, fam. nov. 



Sporangia without columella or capillitium, and the upper part of 

 the coarse sporangium wall replaced by a delicate membrane having 

 a defined outline. 



ORCADELLA, gen. nov. 



Sporangia with coarse stipes; sporangium wall likewise coarse, 

 but at the top of the sporangium replaced by a delicate membrane 

 which forms a more or less flattened deciduous lid. 



Orcadella operculata Wing., sp. nov. 



Sporangia stipitate, without columella or capillitium, very varia- 

 ble in form, barrel-shaped, urn -shaped, 

 vase-shaped, jar-shaped, ovoid or nearly 

 globose, or all varieties appearing in 

 one small group ; running from M. 

 0-05 to M. 0-25 in diameter by M. 01 

 to M. 0"3 in length. Stipe slightly 

 tapering, erect or bent, blackish, rough 

 and coarse from deposits of plasmodic refuse ; very variable in 

 height, from M. 0*375 to M. 1*25. 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 retic- 

 ulately wrinkled. Mass of spores yellowish. Individual spores 

 almost colorless, globose or irregularly roundish, smooth 8-11 mill, in 

 diameter. 



On the trunks of living red-oak trees (Quercus rubra). 

 Fairmount Park and Chestnut Hill, Philada., and also Maine 

 (Harvey). Type in Herb. Acad. Xat. Sci. Philada. 



This plant has been very common this year in Fairmount Park on 

 living red-oak trees, owing to the unusual amount of rain. It gener- 



