256 Mycetozoa of North America 



few attachments; thickenings on the threads in the form of half- 

 rings and numerous spines. Spores gray in mass, 6-8 /n diam., 

 with a few scattered warts. 



Type locality: Philadelphia, Pennsylvania. 



Habitat: On dead wood. 



Distribution: Florida, Iowa, Kansas, New York, *Oregon, 

 Pennsylvania, ^Wisconsin. 



Illustration: Macbr. & Martin, Myxomycetes pi. 17, figs. 

 446^449. 



This form is practically the same as ^. nutans, except that the 

 color is gray, and strangely enough nearly all specimens turn to 

 yellow throughout with long exposure to sunlight. Minor dif- 

 ferences in the markings of the capillitium are of little importance, 

 as they may be found in nearly every species of the genus. A. 

 magna var. rosea was proposed by Rex on a roseate form which he 

 regarded as a variety of A. magna. It has not been found again 

 so far as I know. Lister found the roseate form to have fragments 

 of the evanescent peridium attached to the capillitium and placed 

 it with A. Oerstedtii, at the same time including the gray form. 

 A. magna does not occur regularly in any particular area, appear- 

 ing only now and then. 



13. Arcyria Oerstedtii Rost. Mon. 278. 1875. 



Plasmodium watery white (Lister). Sporangia stalked, clus- 

 tered, cylindrical, curved, arising from a colorless membranous 

 hypothallus, when unexpanded 0.6 to 1.5 mm. high, 0.3 to 0.5 mm. 

 broad, dull crimson; sporangial wall evanescent above or per- 

 sistent as a few, small, well-defined, rounded plates, which are 

 papillose on the inner side, smooth on the margin, and attached 

 to the capillitium; cup membranous, faintly reticulate, and 

 marked with scattered papillae, the rim smooth. Stalks pale red, 

 varying in length, usually short, weak, filled with spore-like cells. 

 Capillitium an elastic network of pale reddish threads 3-5 /x diam., 

 expanding into a long, drooping, cylindrical column; thickenings 

 in the form of half-rings and sharp spines 1-3 n long, arranged in 

 a loose spiral, elsewhere marked with scattered spinules and often 

 with four or five faint, irregular, spiral lines, some threads at- 

 tached to the persistent plates of the sporangial wall, others to the 

 cup; free ends with spinulose tips sometimes present. Spores 

 pale reddish, nearly smooth, marked with a few scattered warts, 

 7-8 ju diam. 



