Sporangia distinct, sessile, densely crowded, sub-rotund reniform more often elongate, interwoven; peridium double; the outer rather thick, calcareous, yellow, or yellowish white, the inner thin, yellowish; capillitium white, containing numerous large, irregular calcareous granules; columella none; spores deep violet, 11–13 µ, covered with minute spinules.
This singular species occurs not rarely upon the bark of fallen twigs, upon bits of straw or grass-stems lying undisturbed upon the ground. In such a position the slime-mould covers, as with a sheath, the entire substratum. The outer peridium, especially its upper part, is entirely evanescent, our Fig. 3 shows the sporangia with upper outer peridium wanting. Not rare in summer and autumn.
New England, New York, Pennsylvania, Ohio, Wisconsin, Illinois, Iowa, Colorado, Oregon, Nicaragua.
10. Physarum conglomeratum (Fr.) Rost.
- 1803. Spumaria granulata Schum., Enum. Pl. Saell., II., p. 196, No. 1419.
- 1803. Spumaria minuta Schum., l. c.
- 1829. Diderma granulatum Schum., Fries, S. M., III., p. 110.
- 1829. Diderma minutum Schum., Fries, l. c., p. 111.
- 1829. Diderma conglomeratum Fries, l. c., p. 111.
- 1875. Physarum conglomeratum (Fr.) Rost., Mon., p. 108.
- 1892. Physarum rostafinskii Massee, Mon., p. 301.
- 1894. Physarum conglomeratum Rost., Lister, Mycetozoa, p. 58.
- 1899. Physarum conglomeratum (Fr.) Rost., Macbr., N. A. S., p. 31.
- 1911. Physarum conglomeratum Rost., List., Mycetozoa, 2nd ed., p. 80.
Sporangia depressed, globose, or irregular, sessile, more or less aggregated, ochraceous-yellow, peridium double, the outer, thick, cartilaginous, at length irregularly ruptured, and reflexed, disclosing the more delicate, ashen-gray, inner membrane which encloses capillitium and spores; capillitium abundant, showing large, white irregular calcareous thickenings which are often consolidated in some sporangia tend to aggregate at the centre; spore-mass brown, spores violaceous, slightly roughened, 8–10 µ.
This beautiful species shows a peridium as distinctly double as in any diderma. The outer peridium is reflexed exactly as in some species of that genus; is yellow without, white within, and withal long persistent. The capillitium of course distinguishes the species instantly as a physarum. By the size of the spores it is distinguished from the species preceding. This being a decisive specific character the synonymy prior to Rostafinski is somewhat uncertain. The specific name adopted by the Polish author is therefore approved, although perhaps not the earliest.
Rare. The only specimens thus far are from Tennessee and Louisiana.
11. Physarum mortoni Macbr. n. s.
[Plate XX]., Figs. 2, 2 a.