1797. _Didymium testaceum_ Schrad., _Nov. Gen. Plant._, p. 25. 1801. _Diderma testaceum_ Persoon, _Syn._, p. 167. 1873. _Chondrioderma testaceum_ (Schrad.) Rost., _Vers._, p. 13. 1874. _Diderma mariae-wilsoni_ Clinton, _Rep. N. Y. Mus._, XXVI., p. 74. 1899. _Diderma testaceum_ (Schrad.) Pers., Macbr., _N. A. S._, p. 99. 1911. _Diderma testaceum_ Pers., List., _Mycetozoa, 2nd ed._, p. 106. Sporangia gregarious, sessile, depressed-spherical or sometimes elongate, small, 1 mm. or less, rose-white, smooth, the outer peridium crustaceous, rather thick and persistent, polished, slightly raised above the inner, which is dull ashen and more or less wrinkled; hypothallus none; columella prominent, hemispherical in the typical rounded forms, slightly rough, reddish or reddish alutaceous; capillitium usually abundant, of slender, delicate pale or colorless threads, little branched, and smooth; spores violaceous-brown, minutely roughened, 8-9 mu. A very beautiful species occurring at the same time as the preceding and in similar situations. All our specimens from the west are on dead leaves of oak; some eastern gatherings are on moss. Easily recognized when fresh by its delicate pink or roseate color; weathered specimens are white, and might be confused with forms of _D. reticulatum_, but the sporangia in the present species are less flattened and only rarely in special situations run off to linear or plasmodiocarpous shapes characteristic of _D. reticulatum_. Not common, although widely distributed from east to west. New England, New York, New Jersey, South Carolina, Ohio, Illinois, Iowa, Nebraska, California (_Harkness_), Washington, Oregon. 8. DIDERMA NIVEUM (_Rostafinski_) _Macbr._ PLATE XVIII., Fig. 11 and 11 _a_ 1875. _Chondrioderma niveum_ Rost, _Mon._, p. 170. 1877. _Diderma albescens_ Phillips, _Grev._, V., p. 114. Sporangia gregarious, scattered, or more often crowded, sessile, depressed-spherical, sometimes ellipsoidal or elongate, white, the outer peridium crustaceous, chalky, smooth and fragile, the inner distinct, delicate, ochraceous; hypothallus scant or none; columella well developed, globose or hemispherical, orange-tinted or ochraceous; capillitium abundant, made of threads of two sorts, some purplish or dusky, with pale extremities, uneven, others more delicate and colorless, and with wart-like thickenings, all sparingly branched; spores violet-brown, minutely roughened, 9-10 mu.