This species was in the previous edition distinguished from the Rostafinskian P. reticulatum with spores a little smaller, 6–8 µ, and with a much stronger tendency to the formation of definite sporangia, elongate indeed and branching but often globose or depressed globose. This we may know as,
Var. reticulatum Rost.
- 1875. Chondrioderma reticulatum Rost., Mon., p. 170.
- 1894. Diderma reticulatum (Rost.) Morg., Jour. Cin. Soc., p. 71.
Sporangia gregarious, generally rounded, not much depressed, flat, sometimes, especially toward the margin of a colony, elongate, venulose or somewhat plasmodiocarpous, dull white, the inner peridium ashen or bluish, remote from the calcareous crust, which is extremely fragile, easily shelling off; columella indistinguishable from the base of the sporangium, thin, alutaceous; capillitium of short, generally colorless, delicate, sparingly branching or anastomosing threads perpendicular to the columella; spores black in mass, by transmitted light violet-tinted, smooth, 6–8 µ.
Perhaps our most common form. Found in fall on dead twigs, leaves, etc. Recognized by its rather large, white, depressed or flattened sporangia tending to form reticulations, and hence suggesting the name. The lines of fruiting tend to follow the venation of the supporting leaf; where the sporangium is round, the columella is a distinct rounded or cake-like body; where the fruit is venulose, the columella is less distinct.
By these rounded forms we pass easily, as by a gate, to D. hemisphericum, which, when wholly sessile, differs still in greater diameter of the sporangia and in having somewhat larger spores. Usually in such case the compared colony will show somewhere a very short and stout but very real stipe supporting the discoid fruit.
Rostafinski divided the genus Chondrioderma, i. e. Diderma, into three sections:—
Monoderma to include those species in which the calcareous crust is less distinct or connate with the true peridium.
Diderma, in which the two structures were plainly separate.
Leangium, used as in the present work. In his first section Rostafinski placed C. reticulatum and C. michelii; in the second, C. difforme and C. calcareum.