The Myxomycetes of the Miami Valley, Ohio.

by A. P. Morgan.

MYXOMYCETES, Wallr.

Fructification essentially a minute membranaceous vesicle, the SPORANGIUM inclosing the SPORES, the product of a motile protoplasmic body called the PLASMODIUM.

Microscopic organisms with the habit of the Fungi. The ripe spore of the Myxomycetes is globose or ellipsoidal in shape, with the epispore colorless or colored, and smooth or marked by characteristic surface--sculpture according to the species; the spore in germination gives rise to an elongated protoplasmic body, which exhibits amoeboid movements, and is known by the name of _swarm-cell_. The swarm-cells multiply by bipart.i.tion, which may be repeated through several generations; they then unite together to form the large motile protoplasmic bodies named _plasmodia_. The newly-formed plasmodium is distinguished by its greater size from the swarm-cells, while it exhibits essentially the same movements and changes of shape. The plasmodia gradually increase in size, and as they grow a.s.sume commonly the form of branched strands; these spread over the surface of the substratum, which is usually the decaying parts of plants, in the form of veins and net-works of veins, giving rise to a copiously-branched reticulated or frill-like expansion, which covers surfaces varying in extent from a few to several centimeters. They are chiefly composed of a soft protoplasm of the consistence of cream, which may be readily spread out into a shapeless smear, and is usually colorless, but sometimes exhibits brilliant colors of yellow, orange, rose, purple, etc. The development of the plasmodium ceases with the formation of the _spores_ within their _sporangia_.

The formation of the sporangia out of the plasmodium appears under three general forms, which, however, pa.s.s into each other and are, therefore, not strictly limited.

_First:_ An entire plasmodium spread out on its substratum becomes transformed into a sporangium, or it divides into a variable number of unequal and irregular pieces, each of which undergoes transformation.

Such a sporangium lying flat on the substratum, more or less elongated and flexuous, often branched and reticulate, is termed a _plasmodiocarp_.

_Second:_ Erect sporangia on a narrow or stalk-like base, begin as node-like swellings on the branches of the plasmodium, and gradually rise to their ultimate form as the surrounding protoplasm flows into them and a.s.sumes an upward direction. These sporangia are nearly always perfectly regular in shape; they may be globose, obovoid, somewhat depressed, or more or less elongated, and are either stipitate or sessile.

_Third:_ A number of plasmodia collect together from every side and become fused into a single body, often of considerable dimensions; from these combinations originate the large spore-receptacles which are called _aethalia_. The component sporangia may be regular in shape, standing close together, in a single stratum, with entire connate walls; more often, being elongated and flexuous, they branch and anastomose freely, their walls becoming perforated and more or less defective; in other cases, the aethalium is a compound plasmodiocarp, the narrow sinuous sporangia branched and anastomosing in all directions, forming an intricate network, closely packed together and inseparable. The surface of the aethalium is often covered by a continuous layer of some excreted substance, which is called the _common cortex_.

The wall of the sporangium, typically, is a thin, firm membrane, colorless and pellucid, or colored in various shades of violet, brown, yellow, etc.; it is sometimes extremely delicate, as in Lamproderma, or is scarcely evident, as in Stemonitis; in other instances it is thickened by deposits on the inner surface, as in Tubulina, or by incrustations on the outer surface, as in Chondrioderma. The stipes are tubes usually with a thick wall, which is often wrinkled and folded lengthwise, and is confluent above with the wall of the sporangium; in some cases the stipe also enters the sporangium, and is more or less prolonged within it as a _columella_. The stipe commonly expands at the base into a membrane, which fastens it to the substratum, and is called the _hypothallus_; when all the stipes of the same group of sporangia stand upon a single continuous membrane, it is called a _common hypothallus_.

In the simplest forms, the cavity of the sporangium is filled exclusively with the numerous spores; but in most all of the genera, tubules or threads of different forms occur among the spores and const.i.tute the _capillitium_. The capillitium first makes its appearance in Reticularia, in which upon the inner surface of the walls of the sporangia there are abundant fibrous thickenings; next in Cribraria it is spread over the inner surface of the wall, and is early separated from it; here, also, it first a.s.sumes a more definite form and arrangement; in Physarum it is in connection with the wall of the sporangium only by its extremities while it traverses the interior with a complicated network; in Stemonitis and its allies the capillitium originates wholly from the columella; in most species of Arcyria it issues from the interior of the stipe. The capillitium in Trichia consists of numerous slender threads which are _free_, that is, are not attached in any way; they are usually simple and pointed at each extremity; the surface of these threads exhibits beautiful spiral markings.

ORDER I. LICEACEae.

Sporangia always sessile, simple and regular or plasmodiocarp, sometimes united into an aethalium. The wall a thin, firm, persistent membrane, often granulose-thickened, usually rupturing irregularly. Spores globose, usually some shade of umber or olivaceous, rarely violaceous.

The species of this order are the simplest of the Myxomycetes; the sporangium, with a firm, persistent wall contains only the spores. There is no trace of a capillitium, unless a few occasional threads in the wall of Tubulina prefigure such a structure. To the genera of this order is appended the anomalous genus Lycogala, which seems to me better placed here than elsewhere.

TABLE OF GENERA OF LICEACEae.

1. LICEA. Sporangia simple and regular or plasmodiocarp, gregarious; hypothallus none.

2. TUBULINA. Sporangia cylindric, or by mutual pressure becoming prismatic, distinct or more or less connate and aethalioid, seated upon a common hypothallus.

3. LYCOGALA. aethalium with a firm membranaceous wall; from the inner surface of the wall proceed numerous slender tubules, which are intermingled with the spores.

I. LICEA, Schrad. Sporangia sessile, simple and regular or plasmodiocarp, gregarious, close or scattered; hypothallus none; the wall a thin, firm membrane, sometimes thickened with scales or granules, breaking up irregularly and falling away or dehiscent in a regular manner. Spores globose, variously colored.

The sporangia are not seated on a common hypothallus; they are, consequently, more or less irregularly scattered about on the substratum.

1. LICEA VARIABILIS, Schrad. Plasmodiocarp not much elongated, usually scattered, sometimes closer and confluent, somewhat depressed, the surface uneven or a little roughened and not shining, reddish-brown or blackish in color; the wall a thin, firm pellucid membrane, covered by a dense outer layer of thick brown or blackish scales, rupturing irregularly. Spores in ma.s.s pale ochraceous, globose or oval, even or nearly so, 13-16 mic. in diameter.

Growing on old wood. Plasmodiocarp 1-1.5 mm. in length, though sometimes confluent and longer. The wall is thick and rough, not at all shining.

It is evidently the species of Schweinitz referred to by Fries under this name.

2. LICEA LINDHEIMERI, Berk. Sporangia sessile, regular, globose, gregarious, scattered or sometimes crowded, dark bay in color, smooth and shining; the wall a thin membrane with a yellow-brown outer layer, opaque, rupturing irregularly. Spores in ma.s.s bright bay, globose, minutely warted, opaque, 5-6 mic. in diameter.

Growing on herbaceous stems sent from Texas. Sporangia about .4 mm. in diameter. The bright bay ma.s.s of spores within will serve to distinguish the species. The thin brown wall appears dark bay with the inclosed spores.

3. LICEA BIFORIS, Morgan, n. sp. Sporangia regular, compressed, sessile on a narrow base, gregarious; the wall thin, firm, smooth, yellow-brown in color and nearly opaque, with minute scattered granules on the inner surface, at maturity opening along the upper edge into two equal parts, which remain persistent by the base. Spores yellow-brown in ma.s.s, globose or oval, even, 9-12 mic. in diameter. See Plate III, Fig. 1.

Growing on the inside bark of Liriodendron. Sporangia .25-.40 mm. in length, shaped exactly like a bivalve sh.e.l.l and opening in a similar manner. I have also received specimens of this curious species from Prof. J. Dearness, London, Canada.

4. LICEA PUSILLA, Schrad. Sporangia regular, sessile, hemispheric, the base depressed, gregarious, chestnut-brown, shining; the wall thin, smooth, dark-colored and nearly opaque, dehiscent at the apex into regular segments. Spores in the ma.s.s blackish-brown, globose, even, 16-18 mic. in diameter.

Growing on old wood, Sporangium about 1 mm. in diameter. On account of the color of the spores the genus _Protoderma_ was created for this species by Rostafinski. It is number 2,316 of Schweinitz's N. A. Fungi.

II. TUBULINA, Pers. Sporangia cylindric, or by mutual pressure becoming prismatic, distinct or more or less connate and aethalioid, the apex convex, seated upon a common hypothallus; the wall a thin membrane, minutely granulose, firm and quite persistent, gradually breaking away from the apex downward. Spores abundant, globose, umber or olivaceous.

The sporangia usually stand erect in a single stratum, with their walls separate or grown together: in the more compact aethalioid forms, however, the sporangia, becoming elongated and flexuous, pa.s.s upward and outward in various directions, branching and anastomosing freely. See Plate III, Figs. 2, 3, 4.

1. TUBULINA CYLINDRICA, Bull. Sporangia cylindric, more or less elongated, closely crowded, distinct or connate, pale umber to rusty-brown in color, seated on a well developed hypothallus; the wall thin, firm, with minute veins and granules, semi-opaque, pale umber, often iridescent. Spores in ma.s.s pale umber to rusty-brown, globose, most of the surface reticulate, 6-8 mic. in diameter.

Growing on old wood, mosses, etc. aethalium circular or irregular in shape, from one to several centimeters in extent, the individual sporangia 2-4 mm. in height. Plasmodium at first milky-white, soon changing to bright red, then to umber, becoming paler when mature and dry.

2. TUBULINA CASPARYI, Rost. Sporangia more or less elongated, closely crowded and prismatic, connate, pale umber to brown in color, seated on a conspicuous hypothallus; the wall thin, firm, minutely granulose, semi-opaque, pale umber, iridescent when well matured; all or many of the sporangia traversed by a central columella, from which a few narrow bands of the membrane stretch to the adjacent walls. Spores in the ma.s.s pale umber to brown, globose, the surface reticulate, 7-9 mic. in diameter.

Growing on old prostrate trunks. aethalium two or three to several centimeters in extent, the individual sporangia 3-5 mm. in height.

Plasmodium white, the immature sporangia dull-gray tinged with sienna color. The columella, with its radiating bits of membrane, is the same substance as the wall; it may be a reentrant edge of the prismatic sporangium, caused by excessive crowding together; at least, this may be regarded as its origin; there may have arisen some further adaptation.

The species is _Siphoptychium Casparyi_, Rost. I am indebted to Dr.

George A. Rex for the specimens I have examined.

3. TUBULINA CaeSPITOSA, Peck. Sporangia short-cylindric, closely crowded, distinct or connate, argillaceous olive to olive-brown in color, seated on a well-developed hypothallus; the wall a thin membrane, with a dense layer of minute dark-colored round granules on the inner surface. Spores argillaceous olive in the ma.s.s, globose, minutely warted, 6-8 mic. in diameter.

Growing on old wood. aethalium in irregular patches sometimes several centimeters in extent, the single sporangia about 1 mm. in height.

Plasmodium dark olivaceous, the sporangia blackish if dried when immature, taking a paler shade of olivaceous, according to development and maturity. This is _Perichaena caespitosa_, Peck, in the 31st N. Y.

Report.

III. LYCOGALA, Mich. aethalium with a firm membranaceous wall; from the inner surface of the wall proceed numerous slender tubules, which are intermingled with the spores. The material of the wall appears under three different forms: the inner layer is a thin membrane, uniform in structure, of a yellow-brown color, and semi-pellucid; the outer layer consists of large flat roundish or irregular vesicles, brown in color, filled with minute granules, and arranged in one or more strata; from these vesicles originate the tubules, which traverse the wall for a certain distance, and then enter the interior among the spores; the tubules are more or less compressed, simple or branched, and the surface is ornamented with warts and ridges, which sometimes form irregular rings and reticulations.

If the sporoph.o.r.es in this genus be regarded as simple sporangia, which is the view that Rostafinski takes of one of the species, the tubules are simply the peculiar threads of a capillitium. If, however, the aethalium is a compound plasmodiocarp, the tubules stand for the original plasmodial strands and, consequently, represent the component sporangia.

1. LYCOGALA CONIc.u.m, Pers. aethalia small, ovoid-conic, gregarious, sometimes close together with the bases confluent, the surface pale umber or olivaceous marked with short brown lines, regularly dehiscent at the apex. The wall thin; the outer layer not continuous, the irregular brown vesicles disposed in angular patches and elongated bands, which have a somewhat reticulate arrangement. The tubules appear as a thin stratum upon the inner membrane; they do not branch, and they send long slender simple extremities inward among the spores. Spores in ma.s.s pale ochraceous, globose, minutely warted, 5-6 mic. in diameter.

See Plate III, Fig. 5.

Growing on old wood. aethalium 2-5 mm. in height, the tubules 3-8 mic. in thickness. This is _Dermodium conic.u.m_ of Rostafinski's monograph, but the structure is essentially the same as in the other species. Ma.s.see evidently did not have specimens of this species. I have never seen any branching of the tubules either in the wall or in the free extremities of the interior.

2. LYCOGALA EXIGUUM, Morg. n. sp. aethalia small, globose, gregarious, the surface dark brown or blackish, minutely scaly, irregularly dehiscent. The wall thin; the vesicles with a dark polygonal outline, disposed in thin irregular reticulate patches, which are more or less confluent. The tubules appear as an interwoven fibrous stratum upon the inner membrane; they send long slender branched extremities inward among the spores. Spores in ma.s.s pale ochraceous, globose, nearly smooth, 5-6 mic. in diameter. See Plate III, Fig. 6.