364 PROCEEDINGS OF THE ACADEMY OF [1893. 



NEW NORTH AMERICAN MYXOMYCETES. 

 BY GEO. A. REX, M. D. 



The Myxomycetes described in this paper are in part new and 

 hitherto undescribed species, and in part well marked and stable 

 varieties of existing species. 



Ophiotheca wrightii B. &C. var. stipitata n. var. 



Sporangia stipitate, reniform, globose or ellipsoidal ; stipes vari- 

 able in height, sometimes mere plasmodic thickenings of the bases of 

 the sporangia, sometimes attaining through intermediate grades a 

 height of "5 mm., slightly tapering from below upward, of medium 

 thickness, black, and granulose or occasionally rugose on the surface ; 

 capillitium deep yellow, freely branched and combined to form a 

 long loosely meshed net ; threads provided with scattered short, 

 sharp and either straight or slightly curved spines ; spores yellow, 

 10-12/j. in diameter delicately spinulose. 



Fairmount Park, Philadelphia, Pa. (Harold Wingate.) 



This very unusual and interesting variety is probably the first 

 recorded instance of a stipitate species occurring in the Perichoenacese. 



It differs from the typical form of the species in the presence of 

 stipes, in the closer meshes of the net of the capillitium, and in the 

 shorter spines on the threads of the capillitium. 



The sporangia, however, excepting the stipes, are similar in every 

 respect to the globose and reniform sporangia of the ordinary sessile 

 form. 



Arcyria magna n. sp. 



Sporangia shortly stipitate, densely aggregated, growing either in 

 small clusters or in large effused masses many square inches in area; 

 individual sporangium elongated, cylindrical, tapering toward the 

 end, evanescent above with a small, pale yellowish-gray, funnel- 

 shaped permanent base or calyculus ; inner surface of calyculus 

 smooth, except very rarely a few scattered spinules are found under 

 high amplification ; stipes one mm. in height, tubular, the cavity 

 being filled with rounded plasmodic masses; capillitium much 

 elongated, about 12 mm. in length relaxed, drooping, tawny gray or 

 drab in color, attached slightly by a few threads to the bottom of the 

 calyculus, and forming a loose large-meshed network ; threads of 

 capillitium cylindrical, of uniform thickness, coarsely sculptured 



