19. DIDERMA RUGOSUM (_Rex_) _Macbr._ PLATE XVIII., Fig. 10. 1893. _Chondrioderma rugosum_ Rex, _Proc. Phil. Acad._, p. 369. Sporangia gregarious, scattered, white or ashen, rugulose over the whole surface, the ridges marking the lines of subsequent rupture or dehiscence, the peridium thin papyraceous, stipitate; stipe well developed about equal to the sporangium, subulate, almost black; hypothallus none; columella distinct, generally white, sometimes small, globose, sometimes penetrating the sporangium, to one-half the height; capillitium white or colorless, the filaments freely forked and combined by lateral branches into a loose network attached to the columella and basal wall below and the upper sporangial wall above; spores violaceous-brown, warted, 8-10 mu. This species is well designated _rugosum_, and is recognizable at sight by its wrinkled, areolate surface. Related to _D. radiatum_ in the prefigured dehiscence, but otherwise very distinct. Liable to be overlooked as a prematurely dried physarum. Rare. Plasmodium gray. North Carolina, Iowa. =4. Lepidoderma= _DeBary_ 1858. _Lepidoderma_ DeBy., MS. Rost., _Versuch_, p. 13. Sporangia stalked or sessile; peridium cartilaginous, adorned without with large calcareous scales, superficial or shut in lenticular cavities; capillitium non-calcareous.[33] =Key to Species of Lepidoderma= _A._ Sporangia stipitate, stipe brown 1. _L. tigrinum_ _B._ Sporangia sessile, plasmodiocarpous, spores 10-12 mu 2. _L. carestianum_ _C._ Sporangia plasmodiocarpous, spores 8-10 mu 3. _L. chailletii_ 1. LEPIDODERMA TIGRINUM (_Schrad._) _Rost._ PLATE XIV., Fig. 7. 1797. _Didymium tigrinum_ Schrad., _Nov. Gen. Plantarum_, p. 22. 1873. _Lepidoderma tigrinum_ (Schrad.) Rost., _Versuch_, p. 13. Sporangia scattered, rather large, hemispherical-depressed, stipitate, umbilicate beneath, the peridium shining, olivaceous or purplish, tough, covered more or less abundantly with angular scales; the stipe stout, furrowed, dark brown, but containing calcareous deposits withal, tapering upward, and continued within the peridium as a pronounced more or less calcareous columella; hypothallus more or less prominent, yellowish or brownish; capillitium dark, purplish-brown, of sparingly branching threads radiating from the columella; spores dull purplish-brown, minutely roughened, 10-12 mu. A singular species, rare, but easily recognized by its peculiar, placoid scales, large and firmly embedded in the peridial wall. The internal structure is essentially that of _Diderma_ or _Didymium_. The species occurs in hilly or mountainous regions, on moss-covered logs. The plasmodium pale yellow, some part of it not infrequently remains as a venulose hypothallus connecting such sporangia as are near together. New England to Washington and Oregon; Vancouver Island. 2. LEPIDODERMA CARESTIANUM (_Rabenh._) _Rost._