VOL. XVI. PLATE XII.]

Reprint from THE JOURNAL OF THE CINCINNATI SOCIETY OF NATURAL HISTORY, August, 1896.

THE MYXOMYCETES OF THE MIAMI VALLEY, OHIO.

BY A. P. MORGAN.

Fourth Paper.

(Read May 6, 1896.)

ORDER VIII. PHYSARACEae.

Sporangia simple and stipitate or sessile, sometimes plasmodiocarp, rarely combined into an aethalium; the wall a thin membrane, usually with an outer layer of minute roundish granules of lime. Stipe present or often wanting, seldom prolonged within the sporangium as a columella.

Capillitium consisting of slender tubules, which branch repeatedly in every direction and anastomose to form an intricate network, the extremities attached on all sides to the wall of the sporangium; the tubules more or less expanded at the angles of the network and inclosing minute roundish granules of lime, these granules either aggregated into nodules with intervening empty s.p.a.ces or more rarely distributed throughout their entire length. Spores globose, very rarely ellipsoidal, violaceous.

This order is at once distinguished from the Didymiaceae by the presence of the granules of lime in the capillitium.

TABLE OF GENERA OF PHYSARACEae.

I. Tubules of the capillitium having the granules of lime in them aggregated into roundish or angular nodules, with intervening empty s.p.a.ces.

_A. Outer surface of the sporangium dest.i.tute of lime._

1. ANGIORIDIUM. Plasmodiocarp laterally compressed, splitting regularly into two valves.

2. CIENKOWSKIA. Plasmodiocarp terete, elongated, irregularly dehiscent.

3. LEOCARPUS. Sporangia subglobose or obovoid, stipitate or sessile.

_B. Outer surface of the sporangium invested with granules of lime._

_a. Stipe prolonged within the sporangium as a columella._

4. PHYSARELLA. Sporangium oblong, stipitate, the apex re-entrant.

5. CYTIDIUM. Sporangium globose, stipitate, the apex convex.

_b. Stipe never entering the sporangium._

6. CRATERIUM. Sporangium obovoid to cylindric, stipitate.

7. PHYSARUM. Sporangium globose, depressed globose or irregular, stipitate or sessile.

8. FULIGO. Aethalium a compound plasmodiocarp.

II. Tubules of the capillitium with the granules of lime in them distributed throughout their entire length.

9. BADHAMIA. Stipe not prolonged within the sporangium as a columella.

10. SCYPHIUM. Stipe entering the sporangium and prolonged within it as a columella.

I. ANGIORIDIUM, Grev. Plasmodiocarp laterally compressed, more or less elongated and flexuous, attached by the lower margin to the substratum, and, at maturity, regularly dehiscent along the upper margin by a longitudinal fissure; the wall a firm membrane, with the granules of lime forming a reticulate layer on the inner surface. Capillitium a loose, irregular net-work of tubules, extending from side to side, and containing large, irregular nodules of lime. Spores globose, violaceous.

A genus readily distinguished by its laterally compressed plasmodiocarp, splitting lengthwise by a regular fissure. The wall is a single membrane, and there is but a single reticulate layer of lime upon it, which is plainly on the inner surface.

1. ANGIORIDIUM SINUOSUM, Bull. Plasmodiocarp laterally compressed and very much flattened, more or less elongated and flexuous, sometimes confluent and branched or reticulate, without any hypothallus; the wall a more or less thickened and brownish membrane, the inner surface coated with a dense reticulately thickened white layer of lime, and often studded with the white nodules. Capillitium of hyaline tubules, forming a loose irregular net-work, with numerous broad vesicular expansions filled with lime; the nodules white, very large, irregularly lobed, and branched. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old leaves, sticks, mosses, etc. Plasmodiocarp commonly about 1 mm. in height and 1-5 mm. in length, but the size is variable. The color appears to depend upon the thickening of the membrane; when it is thin and pellucid, the color is white or cinereous from the inner layer of lime and the contained spores; with a more thickened membrane, the color becomes ochraceous or brownish. _Physarum bivalve_ Pers. _Physarum sinuosum_ of Rostafinski's monograph.

II. CIENKOWSKIA, Rost. Plasmodiocarp terete, elongated, flexuous, creeping, and reticulate, irregularly dehiscent; the wall a more or less thickened membrane, externally naked, with the granules of lime on the inner surface. Capillitium of slender tubules, combined into an irregular network, attached on all sides to the wall of the sporangium, and bearing everywhere short pointed or uncinate free branchlets; the lime in thin transverse plates and irregular nodules. Spores globose, violaceous.

The peculiar characteristic of this genus is the short free hooked and pointed branchlets of the capillitium.

1. CIENKOWSKIA RETICULATA, A. & S. Plasmodiocarp more or less elongated, curved and flexuous, simple or branched, sometimes confluent and reticulate, breaking away first along the upper surface, leaving an irregular margin. The wall a firm yellow membrane, with thinner hyaline areas and with thicker yellow-brown or red-brown spots; the outer surface without any lime, smooth, and shining; the inner surface with a dense layer of yellow granules raised at intervals into transverse ridges, these are connected with broad thin flat plates of lime which traverse the capillitium, forming imperfect septa to the sporangium.

Capillitium consisting of slender yellow tubules, forming a network of irregular meshes, with slight expansions at the angles and bearing along the sides short pointed or uncinate free branchlets; the tubules containing a few scattered yellow nodules of lime various in size and shape. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter.

Growing on old wood, bark, leaves, etc. Plasmodiocarp in veins .3-.5 mm.

in thickness, sometimes forming a net-work a centimeter or more in extent. This curious Myxomyces seems very rare in America. I have met with it but once. The specimen in the herbarium of Schweinitz, marked _Physarum reticulatum_, is not this species, though it answers well enough to the original description.

III. LEOCARPUS, Link. Sporangia subglobose or obovoid, stipitate or sessile; the wall a more or less thickened membrane, the external surface dest.i.tute of lime, polished and shining, irregularly dehiscent.

Stipe short, poorly developed or sometimes wanting. Capillitium of slender tubules, forming an irregular net-work more or less expanded at the angles; the tubules enlarging at intervals into vesicles, which usually contain nodules of lime. Spores globose, violaceous.

A genus characterized by the form of the sporangia and the smooth and glossy surface of the wall.

1. LEOCARPUS PSITTACINUS, Ditm. Sporangium small globose or somewhat depressed, stipitate or subsessile; the wall a thin membrane, rugulose and iridescent, with thicker red or yellow spots and patches, dest.i.tute of lime. Stipe weak, erect or inclined, variable in length, the base expanded, orange to red in color. Capillitium a dense net-work of tubules, widely expanded at the angles and bearing numerous irregular vesicles, various in size and form, yellow or orange to red in color.

Spores globose, even, dark violaceous, 7-9 mic. in diameter.

Growing on old wood, leaves, etc. The sporangium .5-.6 mm. in diameter, the stipe about the same length or sometimes very short. The sporangia are dull brownish to the naked eye, but when magnified the green, purple, and blue metallic tints of the wall become apparent. There does not appear to be any granules of lime either on the wall or in the capillitium. _Physarum psittacinum_ Ditm.

2. LEOCARPUS CaeSPITOSUS, Schw. Sporangium small subglobose or obovoid to turbinate, somewhat irregular, stipitate or subsessile; the wall a reticulately thickened and fragile membrane, yellow-brown to greenish-yellow or olivaceous in color, externally rugulose and glossy, the inner surface with scales and patches of lime. Stipe short and thick, sometimes nearly obsolete, yellowish or reddish brown, darker below, the base expanded into a small hypothallus. Capillitium a loose irregular net-work of tubules with wide expansions at the angles; the nodules of lime large, numerous, white or yellowish, irregular, with acute angles and pointed lobes. Spores globose, minutely warted, dark violaceous, 9-11 mic. in diameter.

Growing caespitosely or scattered on old wood and mosses. Sporangium .6-.8 mm. in diameter, variable in shape, the stipe usually very short.

_Physarum caespitosum_ Schw., _North American Fungi_. My specimens, some of them, have been referred to _Physarum citrinellum_ Peck; others to _Physarum variabile_ Rex.

3. LEOCARPUS BRUNNEOLUS, Phillips. Sporangium large, globose or somewhat depressed, sessile; the wall a thick yellow-brown membrane, the outer surface naked, smooth, and polished, with a dense white inner layer of granules of lime, dehiscing in a stellate manner, the segments becoming reflexed. Capillitium of tubules forming a dense net-work, with wide expansions at the angles; the nodules of lime very large, numerous, white, angular and irregular. Spores globose, minutely warted, dark violaceous, 8-10 mic. in diameter.

Growing on bark of oak, California (_Harkness._) Sporangium nearly 1 mm.