182 THE MYXOMYCETES 



and generally persist, as Persoon noticed, a long time after the spo- 

 rangium has fallen. The sporangia are at first black; after spore dis- 

 persal pale ferruginous. In shape they vary from ovate to spherical. 

 Sometimes they are umbilicate below, so that a vertical section would 

 be obcordate. Care must be taken to distinguish the present species 

 from blown-out forms of Lamproderma. 



This most common species seems to be also the center of wid- 

 est differentiation. In a valuable paper on the Myxomycetes of 

 Dr. C. H. Peck's herbarium, Dr. Sturgis (1900) points out the vary- 

 ing relationships of a group of surrounding forms. According to his 

 account C. nigra approaches C. laxa at one extreme, C. cequalis, which 

 the Listers enter as varietal here, at the other. However, in the 

 former the more rigid, direct and simple branching from the columella 

 is usually determinative; in the latter the color, form and generally 

 more delicate structure, and a tendency to grow in tufts will serve to 

 distinguish it. 



In this discussion we have assumed as typical the globose sporan- 

 gium, with the variations in the direction of ovate, obovate, ellipsoidal, 

 etc., the capillitium flexuous and more richly anastomosing near the 

 columella. On the drier slopes in the mountains of Colorado specimens 

 are especially abundant, in proper season covering apparently the 

 lower surface of every barkless twig or fallen stem or even entire trees. 

 In such a field one might imagine every possible variation open to 

 observation. Probably such is the case; but as a matter of fact a single 

 small Plasmodium at lower levels will sometimes show greater range 

 of variation than was noted on the mountain side. The cylindric 

 forms were for some reason few, and when noted were short, though 

 often surmounting stems of double the usual length. 



Rostafinski calls this C. friesiana, using the specific name suggested 

 by de Bary. By this name the species was commonly known for many 

 years. It was previously distributed by Rabenhorst as Stemonitis 

 friesiana de Bary, but this name seems not to have been validly pub- 

 lished. More recently some writers prefer C. obtusata Preuss; but 

 C. obtusata Preuss, as figured by that author (Sturm's Deutsch. Fl., 

 pi. 70), is surely more likely Enerthenema papillatum, and the author 

 says in his description "capillitio vertice soli innato." Persoon cer- 

 tainly recognized the species, and his description, though brief, is yet 

 applicable to no other European species. There seems no reason why 

 the name he gave should not be permanently adopted. Rostafinski's 

 figure, pi. XIII, shows an ellipsoidal sporangium, not cylindric. 



A form with very short stipe and large spores, 10-11 fx, was described 

 by Meylan as the var. brachypus. Later, finding the characters con- 



