Part 18

Fig. 43.--Spumaria alba, Bull. a. Æthalium natural size. b. Capillitium and spores as seen by a magnifying power of 500 diameters.

Fig. 44.--Diderma floriforme, Bull. Stipe and columella × 20.

Fig. 45.--Diderma crustaceum, Peck. a. Sporangia crowded on the thick hypothallus, natural size. b. Sporangia × 11. c. Section through outer coat, inner membrane, and columella.

Fig. 46.--Diderma cinereum, Morgan, a. Sporangia growing on a leaf × 3. b. Sporangia × 23. c. Section through the wall and columella.

Fig. 47.--Diderma reticulatum, Rost. Plasmodiocarp growing on leaf × 3.

Fig. 48.--Diderma effusum, Schw. Plasmodiocarp effused on a leaf × 3.

VOL. XVI. PLATE XII.]

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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. PHYSARACEÆ.

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 spaces or more rarely distributed throughout their entire length. Spores globose, very rarely ellipsoidal, violaceous.

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

TABLE OF GENERA OF PHYSARACEÆ.

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

A. Outer surface of the sporangium destitute 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.