Chapter VII: PHYSARUM, Pers. Sporangium globose, depressed globose or irregular,

stipitate or sessile; the wall a thin membrane, with an outer layer of minute roundish granules of lime, irregularly dehiscent. Stipe present or often wanting, never prolonged within the sporangium as a columella. Capillitium of slender tubules, forming an intricate net-work, the extremities attached on all sides to the wall of the sporangium; the tubules more or less expanded at the angles of the net-work, and containing at varying intervals nodules of lime. Spores globose, violaceous.

_Physarum_ is the central genus of the _Physaraceæ_ from which all the others are detached by characters which for the most part are unimportant.

§1. LAPIDIUM. Lime in the Capillitium scanty; the nodules small, roundish, ellipsoidal or fusiform.

_A. Sporangium stipitate._

_a. Sporangia regular._

1. PHYSARUM NUTANS, Pers. Sporangium orbicular, very much depressed, the base concave or umbilicate, stipitate, cernuous; the wall a thin pellucid membrane, thickly covered with minute white or yellow roundish scales of lime, breaking up into irregular fragments, which often remain attached to the capillitium. Stipe long, slender, tapering upward, bent or curved at the apex, longitudinally rugulose, brown or blackish at the base, becoming paler upward and cinereous or whitish at the apex. Capillitium of very slender threads, rising from the base of the sporangium, forming a net-work with much elongated meshes, scarcely expanded at the angles; the nodules of lime white or yellow, ellipsoidal or fusiform, often very small and few in number, sometimes rather large and numerous. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on wood, bark, mosses, etc. A very common species. Sporangium .4-.5 mm. in diameter, the stipe 1-2 mm. in length, the lime-nodules commonly not thicker than the spores, but sometimes from once to twice their diameter. Under this name I have included all the lenticular species of Persoon's Synopsis, _Physarum nutans_, _P. luteum_, _P. viride_ and _P. aureum_. There is no difference in these species, except in the color of the granules of lime; the form of the sporangium and the shape and color of the stipe are the same in all of them. No two authorities agree in the presentation of this species.

2. PHYSARUM CUPRIPES, B. & R. Sporangium orbicular, much depressed, the base umbilicate, stipitate, cernuous; the greater part of the wall thin and delicate, with a scanty covering of yellow granules of lime, becoming naked and then brassy and iridescent, after maturity soon disappearing; the lower basal portion thicker and more persistent, with a layer of small yellow scales of lime. Stipe long, flexuous, bent at the apex, plicate, pale brown to yellow-brown, darker toward the base. Capillitium of slender tubules, forming a dense persistent net-work, more or less expanded at the angles; the lime-nodules small, numerous, yellow, angular and fusiform, below often confluent. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood; rare. Sporangium .4-.5 mm. in diameter, the stipe two or three times this length. The lime nodules are found both on the sides and at the angles of the meshes, and are fusiform or angular accordingly; the lime is scanty above, but in the lower part of the capillitium the nodules sometimes run together into lobed and branched forms. This is _Physarum berkeleyi_ of Rostafinski's monograph.

3. PHYSARUM OBRUSSEUM, B. &. C. Sporangium globose, the base usually slightly flattened or umbilicate, stipitate and cernuous; the wall a thin, violaceous membrane, covered by small, roundish, white or yellow scales of lime, or sometimes naked, splitting irregularly from the apex downward. Stipe long, slender, tapering upward, flexuous, bent or curved at the apex, yellow, yellow-brown, or pale brown. Capillitium of very slender tubules, forming a loose net-work, scarcely expanded at the angles; the nodules of lime small, white or yellow, roundish or obtusely angular, few to numerous, rarely wanting. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood, bark, mosses, etc Sporangium .2-.4 mm. in diameter, the stipe 1-2 mm. in length, the lime nodules when abundant once to twice the diameter of the spores, when scanty very small. This, as I find it growing, is an extremely variable species; I think its various forms and appearances cover such species as _Didymium obrusseum_ B. & C.; _D. tenerrimum_ B. & C.; _Physarum tenerum_ Rex, etc., etc.

4. PHYSARUM NUCLEATUM, Rex. Sporangium globose, stipitate, erect or slightly nodding; the wall a thin, pellucid membrane, thickly covered with minute, white, roundish scales of lime, which are exceptionally sparse or absent, rupturing irregularly. Stipe long, slender, yellowish-white, longitudinally rugulose, tapering upward, expanded at the base into a small hypothallus. Capillitium of very slender tubules, forming a delicate net-work of small meshes, scarcely expanded at the angles; nodules of lime small, not numerous, roundish, white, usually concentrated into a large lump in the center of the sporangium. Spores globose, very minutely warted, violaceous, 6-7 mic. in diameter.

Growing on old wood, bark, etc.; rare. Sporangium .4-.5 mm. in diameter, the stipe two or three times as long, the lime-nodules about the size of the spores. The species much resembles some of the forms of _P. obrusseum_, but is to be distinguished by its central mass of lime and the small spores.

5. PHYSARUM COMPACTUM, Wingate. Sporangium depressed-globose, the base slightly umbilicate, stipitate, cernuous; the wall a thin, violaceous membrane, rugulose and iridescent, studded with large and thick, snow-white, roundish or elliptic scales of lime, at maturity splitting from the apex downward into several segments. Stipe long, rather weak, bent and flexuous, tapering upward, longitudinally rugulose, from snow-white to whitish-ochre and smoky-white, usually brownish at the base, and arising from a thin hypothallus. Capillitium a delicate net-work of very slender threads, with no expansions at the angles; the lime mostly concentrated in one large, snow-white nodule at the center, a few very small, roundish nodules scattered through the net-work. Spores globose, very minutely warted, violaceous, 7-9 mic. in diameter.

Growing on old wood, mosses, etc.; a common species. Sporangium .4-.5 mm. in diameter, the stipe two or three times this length. _Tilmadoche compacta_ Wingate. It is doubtful if _Tilmadoche columbina_ Rost. belongs to this species. According to Lister, _Lepidoderma stellatum_ Massee, is the same as this species, and if it be objected to the name that there is already a _Physarum compactum_ Ehrenberg, it may have to be called _Physarum stellatum_.

_b. Sporangium more or less irregular_.

6. PHYSARUM LEUCOPHÆUM, Fr. Sporangium globose or depressed-globose, more or less irregular, the base never umbilicate, stipitate or subsessile; the wall a thin violaceous membrane, rugulose and iridescent, with a thin coat of small white scales and granules of lime, or sometimes nearly naked. Stipe variable in length, sometimes very short or quite obsolete, occasionally a few of them confluent, wrinkled, and sulcate, brown below, paler or whitish above. Capillitium a dense irregular net-work of slender tubules, more or less expanded at the angles; the nodules of lime white, small, roundish, or angular, few and scattered. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood, bark, leaves, etc. The sporangium .5-.7 mm. in diameter, the stipe about the same length, or shorter, and sometimes wanting. The lime on the wall and in the capillitium is never abundant and sometimes extremely scanty. Rostafinski's presentation of this species applies well to our specimens.

7. PHYSARUM CONNEXUM, Link. Sporangia subglobose, depressed, more or less irregular, sometimes confluent, stipitate, or subsessile; the wall a thin violaceous, or brownish membrane, rugulose, thickly covered with small white roundish scales of lime, which sometimes accumulate so as to make the surface rough and uneven. Stipe short, thick, rugulose, from snow white to smoky or sooty, especially toward the base, sometimes with a scanty calcareous hypothallus. Capillitium a loose net-work of tubules, much expanded at the angles; the nodules of lime small, white, rather numerous, ellipsoidal or fusiform, sometimes confluent and elongated. Spores irregularly globose, minutely warted, dark violaceous, 9-11 mic. in diameter.

Growing on old wood and bark. Sporangium .6-1.0 mm. in diameter, the stipe usually shorter than the diameter, sometimes very short; the lime-nodules about the thickness of the spores. This is a larger and rougher species than _P. leucophæum_, the sporangium is more often irregular and the spores darker colored. _P. confluens_ and _P. connexum_ of Link.

8. PHYSARUM COMPRESSUM, A. & S. Sporangium laterally compressed and much flattened, subreniform, stipitate or subsessile; the wall a thin violaceous or brownish membrane, rugulose, thickly covered with small white roundish nodules of lime, similar to those in the capillitium. Stipe short, brown or blackish at least below, sometimes pallid or grayish above, longitudinally rugulose. Capillitium of slender tubules, forming a loose net-work; the nodules of lime small, white, very numerous, roundish or ellipsoidal, often confluent end to end. Spores irregularly globose or angular, minutely warted, dark violaceous, 11-14 mic. in diameter.

Growing on old stalks and leaves of _Zea mays_. Sporangium variable, .6-1.0 mm. in breadth, the stipe 1 mm. or less in length; the lime nodules about the thickness of the spores. According to Saccardo this species is the same as _Physarum nephroedium_ Rost.

9. PHYSARUM POLYCEPHALUM, Schw. Sporangia confluent into a subspheric gyrose-complicate head, composed of several to many laterally compressed, irregular, simple sporangia; the wall a thin, pellucid membrane, covered by a thin layer of minute scales of lime, white to yellow or greenish-yellow Stripes thin, flat, weak, and often prostrate, pale yellow, more or less connate, arising from a thin hypothallus. Capillitium of slender tubules forming a loose, irregular network, more or less expanded at the angles: the lime-nodules white or yellow, small, fusiform or by confluence elongated and sometimes branched. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old bark, wood, leaves, etc. The sporangia rarely simple, usually confluent into a head of from four or five to fifteen or twenty, and sometimes more, simple sporangia; the stipes variable in length, long or short, rarely wanting. The gray form is _Didymium polymorphum_ Mont., the yellow-green form _D. gyrocephalum_ Mont. Sprengel considered this species the same as _Physarum compactum_ Ehr., and it appears under this name in Schweinitz's _North American Fungi_; but Fries, who had seen specimens of both, disposed of them differently.

10. PHYSARUM DIDERMOIDES, Pers. Sporangia obovoid-oblong, stipitate, growing close together on a white membranaceous common hypothallus; the wall with a thick, white, outer layer of lime, easily crumbling and falling away, leaving the sporangium dark gray; the inner membrane rather thick and firm, violaceous, with a closely adherent layer of granules of lime. Stipes very short, white, thin, and weak, each formed by a bit of membrane arising from the hypothallus. Capillitium a loose net-work of slender threads, bearing numerous roundish or irregular white nodules of lime. Spores irregularly or angularly globose, minutely warted, dark violaceous, 12-15 mic. in diameter.

Growing on wood, leaves, grass, etc. Sporangia .6-1.2 mm. in length by .4-.6 mm. in thickness, the stipe shorter than the sporangia. _Spumaria licheniformis_ Schw., belongs here. This is a truly abnormal species of _Physarum_, so much so that Fries, in the _Summa Veg. Scand._ placed it by itself in a separate genus, _Claustria_.

_B. Sporangia sessile._

11. PHYSARUM CONFLUENS, Pers. Plasmodiocarp roundish, oblong or elongated, and by confluence branched and reticulate; the wall a thin, violaceous membrane, rugulose, with a thin, closely adherent layer of minute granules of lime, over which are scattered small, white, roundish nodules, which sometimes accumulate into a thick, pulverulent coat. Capillitium a loose net-work of tubules, widely expanded at the angles; the nodules of lime small, white, very numerous, roundish or ellipsoidal, by confluence elongated and irregular. Spores irregularly globose, minutely warted, dark violaceous, 9-11 mic. in diameter.

Growing on old wood, bark, leaves, etc. Plasmodiocarp .4-.5 mm. in thickness, varying from roundish to much elongated, creeping and reticulate. The sporangium before dehiscence is gray, whence Link's name, _Physarum griseum_; the loose pulverulent coating of lime easily falls away, leaving the sporangium dark colored, whence Rostafinski's name, _Physarum lividum_. The amount of lime on the wall and in the capillitium is variable.

12. PHYSARUM LUTEOLUM, Peck. Sporangia small, subglobose, sessile, closely gregarious; the wall a thin membrane, covered by a layer of small scales of lime, yellowish, inclining to tawny, in color, rupturing irregularly. Capillitium of slender tubules, forming a dense net-work of small meshes, scarcely expanded at the angles; the nodules of lime small, numerous, yellowish, roundish, or ellipsoidal. Spores globose, nearly smooth, violaceous, about 10 mic. in diameter.

Growing on living leaves of _Cornus canadensis_, Adirondack Mountains, New York. I have not seen a specimen of this _Physarum_, but from Professor Peck's description and figure it seems to be a unique species.

13. PHYSARUM THEJOTEUM, Fr. Sporangia very small, sessile, on a thin membranaceous hypothallus, closely crowded together and more or less connate, subobovoid or oblong, irregular from mutual pressure; the wall a thin violaceous membrane, closely covered with a thin layer of small irregular scales of lime, tawny or yellowish tawny in color, breaking up irregularly about the apex. Capillitium a loose irregular net-work of slender threads, more or less expanded at the angles; the lime nodules small, tawny or yellowish, not numerous, ellipsoidal or fusiform, by confluence elongated and irregular. Spores globose, even, violaceous, 6-7 mic. in diameter.

Growing on old wood, mosses, etc. Sporangia .2-.4 mm. in diameter at the apex, densely packed and their walls grown together, approaching the aethalioid structure; the lime-nodules from one to two or three times the diameter of the spores in thickness. I have described my specimens, which are abundant, very carefully, and judge them to be referable to this species; if so, they show that the species should be kept apart from _Physarum virescens_. _Didymium nectriæforme_ B. & C., is evidently this same species.

14. PHYSARUM LATERITIUM, B. & R. Sporangia sessile, irregularly globose and gregarious, or by confluence more or less elongated and plasmodiocarp; the wall a thin violaceous membrane, rugulose and iridescent, closely covered with small irregular scales of lime, from testaceous or brick-red to bright red in color. Capillitium a dense irregular net-work of tubules, much expanded at the angles; the nodules of lime small, very numerous, roundish or angular, whitish or yellowish, sometimes tinged with red granules. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood, sticks, leaves, etc. Sporangia .4-.6 mm. in diameter, by confluence sometimes much elongated; the lime-nodules two or three times the diameter of the spores in thickness. _Didymium lateritium_ B. & R. _Physarum inequale_ Peck, is the same species.

§2. SAXELLA. Lime in the capillitium abundant, the nodules large, angular or irregular, with pointed lobes and branchlets.

_A. Sporangia stipitate._

15. PHYSARUM IMITANS, Racib. Sporangium depressed-globose, the base flattened or umbilicate, stipitate, erect or cernuous; the wall a thin violaceous membrane, with a closely adherent layer of minute granules, over which are scattered rather large, roundish or irregular white scales of lime, splitting from the apex downward into a few irregular segments. Stipe short, thick at the base and tapering upward, longitudinally rugulose, from gray to brown or blackish, especially below. Capillitium a loose irregular network of tubules, widely expanded at the angles; the nodules of lime white, numerous, large, irregular, with pointed angles and lobes. Spores globose, very minutely warted, violaceous, 8-9 mic. in diameter.

Growing on old wood, mosses, etc. Sporangium .4-.5 mm. in diameter, the stipe about the same length or a little longer. The species superficially resembles the gray form of _Physarum nutans_, and quite likely is constantly overlooked on this account. Although I am not able to verify my reference, yet my specimens answer so well to the description of Raciborski that I am unwilling to invent a new name.

16. PHYSARUM ORNATUM, Peck. Sporangium globose or depressed-globose, stipitate; the wall a thin yellowish membrane, covered with minute granules and small irregular scales of lime, yellow to orange in color. Stipe short, erect, blackish-brown, black at the base, longitudinally plicate, rising from a small hypothallus. Capillitium of tubules forming a rather dense net-work, with wide expansions at the angles; the nodules of lime large, numerous, yellow, irregular, sometimes confluently branched and reticulate. Spores globose, minutely warted, dark violaceous, 10-12 mic. in diameter.

Growing on old wood, bark, mosses, etc. Sporangium about .5 mm. in diameter, the stipe about the same length or shorter. _Physarum oblatum_ McBride, can not be distinguished from this. Specimens of this species in the herbarium of Schweinitz are labeled _Physarum sulphureum_; this is without doubt a mistake.

17. PHYSARUM GRAVIDUM, Morgan, n. sp. Sporangium depressed-globose, the base umbilicate, stipitate; the wall a thin, violaceous membrane, brownish at the base, with a thin coat of small, white scales and minute granules of lime. Stipe long, erect, brown or reddish-brown, darker below, tapering upward, expanding at the base into a small hypothallus. Capillitium of slender tubules forming a loose net-work, more or less expanded at the angles and for the most part filled with lime; the nodules white, slender, much elongated and branched, with pointed lobes and branchlets. Spores globose, very minutely warted, dark violaceous, 11-13 mic. in diameter.

Growing on old stalks of _Zea mays_. Sporangium .5-.6 mm. in diameter, the stipe about twice this length. The lower part of the capillitium is sometimes entirely filled with lime, so that the species approaches Badhamia in the structure of its capillitium.

18. PHYSARUM LEUCOPUS, Link. Sporangium globose, the base slightly flattened, stipitate; the wall a thin, violaceous membrane, with a white, pulverulent outer coat of minute granules of lime. Stipe short, thick, erect, snow-white, longitudinally rugulose, tapering upward, expanding at the base into small, white hypothallus. Capillitium a loose net-work of tubules, with wide expansions at the angles; the nodules of lime large, white, numerous, irregularly lobed and branched. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood, leaves, etc. Sporangium .3-.4 mm. in diameter, the stipe about the same length as the diameter. Our specimens are a smaller form than the European, with smaller and smoother spores. Superficially the species resembles _Didymium squamulosum_, and it is _Didymium leucopus_ of Fries, S. M.

19. PHYSARUM GLAUCUM, Phillips. Sporangium globose, or the base slightly depressed, stipitate; the wall a thin, violaceous membrane, covered with minute, white granules and small roundish or irregular scales of lime. Stipe short, stout, erect, black, longitudinally wrinkled, expanding at the base into a small hypothallus. Capillitium of much-flattened tubules, forming a loose net-work, widely expanded at the angles; the nodules of lime numerous, large, white, irregular, with pointed angles and lobes. Spores globose, very minutely warted, dark violaceous, 12-14 mic. in diameter.

Growing on old leaves: California. Sporangium .5-.7 mm. in diameter, the stipe not longer than the diameter. This is quite a robust species, both externally and in the broad, flat tubules of the capillitium.

20. PHYSARUM RELATUM, Morgan, n. sp. Sporangium globose, the base umbilicate, stipitate, often cernuous; the wall a thin, violaceous membrane, rugulose and iridescent, covered with small, roundish or irregular white scales of lime. Stipe long, erect or inclined, rising from a thin hypothallus, tapering upward, white or cream color to ochraceous. Capillitium a dense net-work of tubules, more or less expanded at the angles, and almost entirely filled with white granules of lime, leaving only here and there short, slender empty spaces. Spores globose, nearly smooth, violaceous, 8-9 mic. in diameter.

Growing on old wood. Sporangium .5-.6 mm. in diameter, the stipe about twice this length. The capillitium is rigid, with the abundance of lime almost as in the genus _Badhamia_. Superficially the species much resembles _Cytidium globuliferum_ or _Physarum compactum_, but the disposition of the lime on the wall and in the capillitium is altogether different.

21. PHYSARUM AURISCALPIUM, Cke. Sporangia subglobose, depressed, substipitate; the wall a hyaline membrane with a thin, closely adherent layer of minute granules of lime, over which are scattered large, irregular, orange-red scales of lime. Stipe very short, sometimes almost obsolete. Capillitium of tubules forming a loose net-work, with widely expanded angles, and mostly filled with orange granules of lime, only here and there short, slender, empty spaces. Spores globose, minutely warted, dark violaceous, 11-13 mic. in diameter.

Growing on rotten wood; South Carolina, Ravenel. Sporangia .6-.8 mm. in diameter, the stipe very short. Described in _Annals of the Lyceum of Natural History of New York_, June, 1877. So fine a species ought to be found again. Cooke's specimen was examined by Lister, _Mycetozoa_, p. 61.

EXPLANATION OF PLATE XIV.

Fig. 56.--Craterium minimum, B. & C. _a._ Sporangia × 5. _b._ Sporangium with lid × 90. _c._ Capillitium and spores × 500.

Fig. 57.--Craterium maydis, Morgan. _a._ Sporangia × 5. _b._ Sporangium × 90. _c._ Capillitium and spores × 500.

Fig. 58.--Physarum obrusseum, B. & C. _a._ Sporangia × 5. _b._ Sporangium × 90. _c._ Capillitium and spores × 500.

Fig. 59.--Physarum connexum, Link. _a._ Sporangia × 5. _b._ Sporangium × 90. _c._ Capillitium and spores × 500.

Fig. 60.--Physarum polycephalum, Schw. _a._ Sporangia × 5. _b._ Sporangia × 90. _c._ Capillitium and spores × 500.

Fig. 61.--Physarum lateritium, B. & C. _a._ Sporangia × 5. _b._ Sporangia × 90. _c._ Capillitium and spores × 500.

Fig. 62.--Physarum imitans, Racib. _a._ Sporangia × 5. _b._ Sporangium × 90. _c._ Capillitium and spores × 500.

Fig. 63.--Physarum relatum, Morgan. _a._ Sporangia × 5. _b._ Sporangia × 90. One divested of the wall and showing the rigid capillitium. _c._ Capillitium and spores × 500.

VOL. XIX. PLATE XIV.

MORGAN ON MYXOMYCETES.]

_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.