For these reasons, _D. globosum_ Pers. may stand, waiting further light from Europe.
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 µ.
Common. Readily to be distinguished from the preceding by the larger spores and more crowded habit. New England west to Nebraska.
The didermas are generally delicately beautiful. The outer wall in the present species is like finest unglazed china, softly smooth, and yet not polished, often absolutely white, with porcellanous fracture. An inter-parietal space separates the outer from the inner wall, so that the former may be broken, bit by bit, without in the least disturbing the underlying structure. The inner wall is ashen or gauzy iridescent green, sending back all colors in reflected light. The spores are violet, deeply so when fresh, the capillitium strong and likewise tinted; the columella passing down and blending with the common snow-white hypothalline base. The distinct habits of the two species are represented in Figs. 5 and 7. In the one the distinct sporangia are associated but not crowded; in the other all are massed together in quite æthalioid fashion, forming circumambient, chalky masses of considerable size, 2 or 3 cm., overcrowded, superimposed, where the sporangia are regular in shape and size by reason of mutual pressure. The plasmodium develops in forests and orchards, among decaying leaves, but is inclined to rise as maturity draws near, to ascend some twig erect, or the stem of a living plant to the height of several inches where the sporangia at length appear "heaped and pent", an encircling sheath, conspicuous after the fashion of a spumaria for which it is indeed sometimes mistaken.