19. DIDYMIUM LEONINUM _Berk. & Br._ 1873. _Didymium leoninum_ Berk. & Br., _Jour. Linn. Soc._, XIV., p. 83. 1876. _Lepidoderma tigrinum_ Rost., _App. to Mon._, p. 23. 1909. _Lepidodermopsis leoninus_ v. Hoehnel, _Sitz. K. Ak. Wiss. Wien, Math. Nat. Ks._, CXVIII., 439. Sporangia gregarious, sub-globose, covered more or less completely with white or yellowish deposits of crystalline lime, stipitate; stipes short, orange or brown, containing lime, enlarged to form the globose orange columella and often connected at base by a venulose hypothallus; capillitium of slender threads, anastomosing, colorless at the tips; spores violet-grey, minutely warted, 7-9 mu. Like _Lepidoderma tigrinum_, but has different calcic crystals. Java and Ceylon. =3. Diderma= _Persoon_ 1794. _Diderma Persoon_, _Roem. N. Mag. Bot._, I., p. 89. 1873. _Chondrioderma_ Rost. _Versuch_, p. 13, _Mon._, p. 167. 1894. _Chondrioderma_ Rost., List., _Mycetozoa_, p. 75. 1899. _Diderma Persoon_, Macbr., _N. A. S._, p. 92. Sporangia plasmodiocarpous or distinct, sessile or stipitate; the peridium as a rule double, the outer wall generally calcareous with the lime granules globular, non-crystalline, the inner wall very delicate and often, in the mature fructification, remote from the outer; columella generally prominent. The genus _Diderma_ is usually easy of recognition, by reason of its double wall, the outer, crustaceous, usually calcareous, and its limits remain substantially as originally set by Persoon. His definition is as follows:-- "Peridium ut plurimum duplex; exterius fragile; interius pellucens, subdistans. Columella magna, subrotunda. Fila parca latentia."--_Syn. Meth. Fung._, p. 168. Rostafinski changed the name of the genus to _Chondrioderma_ (_chondri_, cartilage), seemingly at De Bary's suggestion, and seems to have regarded Persoon's definition as applicable to those species only in which the wall is not only plainly double, but in which the two walls are as plainly remote from each other. More especially he esteemed a new generic name necessary, since he regarded several included species, as _D. spumarioides_, _D. michelii_, etc., monodermic. Since it is doubtful whether any diderma is really monodermic, and since Persoon's definition in any case seems sufficiently elastic, we have seen no reason to discard the older name. Persoon's _Diderma_ when established, _l. c._, included _D. floriforme_. He made some confusion in his later work by admitting some physarums. This induced Schrader to throw all the didermas into his new genus, _Didymium_. According to the nature of the sporangial wall, the species fall rather naturally into two sections:-- _A._ Outer sporangial wall distinctly calcareous, fragile; species generally sessile _Diderma_