There are two ways to meet the difficulty. In the first place it seems probable that a small-spored form really hides somewhere in Europe. The difference between the _Monograph_ measurement and the size admitted for _D. crustaceum_ Pk., evidently considered by Mr. Lister as type and so used in his illustration, Pl. 85, is too great to be esteemed merely an error. That added .3 (Rost.) indicates caution, the average of several measurements. Our _D. globosum_ may represent what the _Monograph_ describes.[32] In the second place we may as American students mistake larger and more globular forms of something else, of _D. spumarioides_ Fr., whose spores are but little larger; or of _D. effusum_ (Schw.) Morg., where the flattened plasmodiocarps anon splatter out to globose drops of polished whiteness, and whose spores are 8 mu. But even here the chances of error are small. In the species last named the columella or sporangial base is alutaceous, not white; in Fries' species, while the columella if present may be white, the peridial walls are different, difficult to distinguish. For these reasons, _D. globosum_ Pers. may stand, waiting further light from Europe. 5. DIDERMA CRUSTACEUM _Peck._ PLATE VII., Fig. 7 1871. _Diderma crustaceum_ Peck, _Rep. N. Y. Mus._, XXVI., p. 74. 1889. _Chondrioderma crustaceum_ (Peck) Berl., _Sacc._, VII., p. 373. Plasmodium at first watery, colorless, becoming at length milky white; sporangia closely crowded or superimposed, in a cushion-like colony, creamy white, globose, imbedded in the substance of the hypothallus, the outer peridium smooth, delicate, crustaceous, fragile, remote from the blue iridescent inner membrane; hypothallus prominent; columella variable, generally present, globose; capillitium dark-colored, the threads branching and combining to form a loose net; spore-mass black, spores by transmitted light dark violaceous, delicately roughened, 12-15 mu. Common. Readily to be distinguished from the preceding by the larger spores and more crowded habit. New England west to Nebraska.