Part 24

B. Sporangia sessile.

22. PHYSARUM PLUMBEUM, Fr. Sporangia small, globose or obovoid, sessile, on a narrow base, gregarious, sometimes close but seldom confluent; the wall a thin violaceous membrane, with a very thin layer of small white scales and minute granules of lime, sometimes naked. Capillitium a loose net-work of slender tubules, with slight expansions at the angles; the nodules of lime white, numerous, more or less elongated, irregularly lobed and branched. Spores globose, even, violaceous, 7-9 mic. in diameter.

Growing on old leaves, sticks, etc. Sporangia .3-.4 mm. in diameter, quite regular in shape, attached by a narrow base, sometimes by a mere point, rarely confluent. The lime on the wall of the sporangium is rather scanty, sometimes altogether absent, and the nodules of lime in the capillitium are rather small. The species is figured by Micheli N. P. G. Tab. 96, Fig. 9. It is named by Fries S. M., III, p. 142. It is figured again by De Bary, Die Mycetozoen, Tafel I.

23. PHYSARUM ATRUM, Schw. Sporangia sessile, subglobose or oblong, by confluence, more or less elongated, bent or flexuous and branched; the wall a thin violaceous membrane, rugulose, covered by a wrinkled and reticulate layer of white granules of lime, which sometimes become thin or disappear. Capillitium a loose net-work of tubules, more or less expanded at the angles; the nodules of lime white, numerous, large, irregularly lobed and branched. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old leaves, bark, grasses, etc.; apparently the most common of these three cinereous species. Sporangia .3-.5 mm. in thickness, some of them roundish or oblong, others elongated to several millimeters. The sporangium is often elegantly reticulate as observed by Schweinitz even when the lime is quite scanty. In Saccardo's Sylloge Berlese changed the name to Physarum reticulatum, but this is unnecessary, as the Physarum atrum of Fries is not a Myxomyces.

24. PHYSARUM CINEREUM, Batsch. Sporangia large, subglobose, sessile, gregarious, sometimes close and confluent; the wall a thin violaceous membrane, with a closely adherent layer of minute granules, over which are scattered irregular white scales of lime. Capillitium of tubules forming a loose net-work, with wide expansions at the angles; the nodules of lime numerous, white, very large, with pointed angles and lobes, by confluence often branched and reticulate, and occasionally forming a pseudo-columella in the center of the sporangium. Spores globose, minutely warted, dark violaceous, 10-13 mic. in diameter.

Growing on old wood, leaves, etc. The sporangia .4-.6 mm. in diameter, more or less irregular. The great abundance of lime in the capillitium and the large distinctly warted spores distinguish this species. Physarum cinereum of Persoon's Synopsis, Didymium cinereum of Fries' Systema. The only American specimens I have of this species are from Iowa (McBride) and from Nebraska (Webber).

25. PHYSARUM VIRESCENS Ditm. Sporangia large, subglobose, irregular and unequal, sessile, gregarious, sometimes crowded, but not often confluent; the wall a thin membrane, violaceous, or in places yellowish, with a dense layer of yellow or greenish-yellow scales and granules of lime. Capillitium a loose net-work of tubules, with wide expansions at the angles; the nodules of lime large, numerous, yellow or greenish-yellow, more or less elongated, lobed, and branched. Spores globose or somewhat irregular, very minutely warted, violaceous, 9-11 mic. in diameter.

Growing on old leaves, mosses, etc. Sporangia .5-.8 mm. in diameter, occasionally by confluence more elongated. Though found in all parts of the country, the species seems rare. This is not the Physarum virescens described by Rostafinski.

26. PHYSARUM RUBIGINOSUM, Fr. Sporangia subglobose, sessile, gregarious; the wall a thin hyaline membrane, thickly covered with large irregular scales of lime, orange to red or dark red in color, breaking up irregularly. Capillitium of hyaline tubules, forming a loose irregular net-work, more or less expanded at the angles; the nodules of lime large, angular, and irregular, sometimes confluent, orange to dark red in color. Spores globose, very minutely warted, dark violaceous, 9-11 mic. in diameter.

Growing on old wood, leaves, mosses, etc. Sporangia .6-.8 mm. in diameter. Physarum fulvum Fries S. M., III, p. 143. A rare species. It should not be confounded with Physarum lateritium.

27. PHYSARUM SERPULA Morgan, n. nom. Plasmodiocarp roundish or oblong to much elongated, bent, annular and flexuous, sometimes by confluence branched and reticulate; the wall a firm yellowish membrane, with a thin, rough, closely adherent coat of granules of lime, dull ochre to lemon-yellow and orange in color. Capillitium a dense net-work of tubules, for the most part filled with lime, only here and there short, slender, empty spaces; the nodules large, numerous, white or yellow, angular and with pointed lobes and branchlets. Spores globose, minutely warted, dark violaceous, 9-11 mic. in diameter.

Growing on leaves, bark, lichens, etc. Plasmodiocarp .3-.4 mm. in thickness and of varying length. This species is in the herbarium of Schweinitz, at Philadelphia, with the name Physarum reticulatum; it is described by George Massee as Physarum gyrosum; by Lister it is incorporated with several other species under Badhamia decipiens.

28. PHYSARUM CONTEXTUM, Pers. Sporangia sessile and closely crowded together, roundish or more or less elongated, flexuous and complicate, the apex plane or impressed; the wall a firm yellowish membrane, covered by a thick pulveraceous layer of lime, white, ochraceous or yellow, easily crumbling and breaking up. Capillitium a loose net-work of tubules, much expanded at the angles; the nodules of lime very large, white or yellow, numerous, angular, and irregular, by confluence lobed and branched, sometimes massed together in the center of the sporangium. Spores globose, minutely warted, dark violaceous, 10-13 mic. in diameter.

Growing on bark, leaves, mosses, etc. Sporangia with a width of .3-.5 mm. and varying in length from .5 mm. to 1 or 2 mm. The sporangia are often so much crowded as to appear to be grown together. Diderma ochroleucum B. & C. belongs to this species. Physarum conglomeratum Fr. is a closely related species, with smaller and smoother spores. I have not met with this.

29. PHYSARUM DIDERMA, Rost. Sporangia large, irregularly globose or oblong, sessile, but without a hypothallus, closely crowded together and sometimes confluent. The wall composed of two distinct and separate layers; the outer a thick, uneven, crustaceous, snow-white layer of lime; the inner a thin, violaceous membrane, cinereous from the adherent granules of lime, or free from them, and iridescent. Capillitium of tubules forming a loose net-work, with wide expansions at the angles; the nodules of lime numerous, snow-white, large, irregular, with pointed angles and lobes, sometimes confluent in the center of the sporangium. Spores globose, minutely warted, dark violaceous, 9-10 mic. in diameter.

Growing on wood, bark, and mosses. Sporangia .8-1.0 mm. in diameter, more or less irregular. The wall of the sporangium is exactly like that of certain species of Diderma. This species must be rare, as I have met with it but twice in ten years, and I am not aware that it has ever been found by any one else.

VIII. FULIGO, Haller. Aethalium a compound plasmodiocarp; the component sporangia branching and anastomosing in every direction, complicate and grown together; the walls of the sporangia a thin membrane, coated with minute, roundish granules of lime. Capillitium of tubules forming a net-work of irregular meshes, more or less expanded at the angles, the tubules containing in greater or less abundance irregular nodules of lime. Spores globose or sometimes ellipsoidal, violaceous.

The genus is readily distinguished from Spumaria by the round granules of lime upon the walls of the sporangia.

§1. AETHALIUM, Link. Aethalia large; the lime in the capillitium scanty, the nodules small, ellipsoidal, or fusiform.

a. Aethalium with a thick fragile common cortex.

1. FULIGO RUFA, Pers. Plasmodium a large soft mass with a peculiar odor and golden yellow in color. Aethalium very large, pulvinate, orbicular, elongated, or quite irregular, extremely friable, the surface tawny or ferruginous to ochraceous and whitish. The long narrow, sinuous sporangia closely compacted, entirely grown together and inseparable, covered by a thick common cortex, and seated on a much thickened hypothallus; walls of the sporangia a thin pellucid membrane, coated by a thin layer of white granules of lime. Capillitium of very slender tubules, extending across from wall to wall, sparingly branched and scarcely forming a network, not at all or only slightly expanded at the angles; the tubules for the most part empty, here and there with slight fusiform or elongated swellings containing granules of lime, occasionally bearing roundish or ellipsoidal nodules of larger size. Spores globose, nearly smooth, violaceous, 6-9 mic. in diameter.

Growing on old trunks in woods in great abundance from early Spring to Winter. Aethalium 3-6 or sometimes many centimeters in extent and 1-2 cm. in thickness. The common cortex and the hypothallus are a millimeter or more in thickness; they are composed of successive layers of thin plates of membrane coated with granules of lime.

b. Aethalium naked, i. e., without a common cortex.

2. FULIGO VIOLACEA, Pers. Plasmodium a soft effused mass, dark red or wine-colored. Aethalium large, pulvinate or effused, orbicular or more or less elongated and irregular, the surface minutely pitted and perforate, furnished with a scanty layer of lime, whitish or yellowish to brick-red in color, leaving naked purple and violet spots and patches, seated on a thin membranaceous brick-red hypothallus. Sporangia long, narrow, and sinuous, closely packed together; the walls a thin violaceous membrane, rugulose and iridescent, with scattered granules, or nearly destitute of lime. Capillitium of slender violet tubules, forming a loose net-work, with slight expansions at the angles; the tubules with numerous rather large vesicular expansions, ellipsoid or fusiform in shape, and scantily furnished with lime. Spores globose, nearly smooth, pale vinous, 6-8 mic. in diameter.

Growing on old trunks in woods; not uncommon in this region. Aethalium 1-3 or more centimeters in extent, and 5-10 mm. in thickness. The vesicles of the capillitium vary from 15-30 or sometimes to 50 mic. in diameter, their inner surface is usually coated by a single layer of granules of lime, they are rarely filled with lime and sometimes are naked entirely; when dry many of them are to be found collapsed.

3. FULIGO FLAVA, Pers. Plasmodium effused lemon-yellow. Aethalium mostly effused, irregular, the surface reticulate, pitted and perforate, entirely naked, pale yellow to lemon-yellow and greenish-yellow, the hypothallus thin or scarcely evident. Sporangia laterally much compressed, flexuous, and gyrose, not everywhere grown together, but forming a dense reticulum; the walls a thin, pellucid membrane, with a dense layer of lemon-yellow granules of lime. Capillitium of short and very slender tubules, sparingly branched and scarcely forming a net-work, not expanded at the angles; the tubules very scantily furnished with lime, in scattered, small, fusiform nodules, white or lemon-yellow. Spores globose, very minutely warted, violaceous, 7-9 mic. in diameter.

Growing on mosses, old leaves, sticks, etc.; not common. Aethalia in irregular patches 2-4 cm. or more in extent, sometimes almost reduced to a simple plasmodiocarp. This species furnishes a clear notion of the structure of the aethalium in the other species, on account of the sporangia being but loosely compacted and not entirely grown together. The Fuligo vaporaria Pers., of the green-houses and gardens I have never seen; the Mucor septicus Linn., was thought to be the plasmodium of this. Linnæus's description is simply "Mucor unctuosus flavus."