Part 20

V. CYTIDIUM, Morgan. Gen. nov. Sporangium globose or rarely ellipsoidal, stipitate; the wall a thin membrane, with an external layer of minute granules of lime, rupturing irregularly. Stipe more or less elongated, tapering upward and entering the sporangium as a columella. Capillitium of slender tubules, arising from the columella, repeatedly branching and anastomosing to form a regular net-work, the extremities attached on all sides to the wall of the sporangium, the tubules containing at intervals nodules of lime. Spores globose, violaceous.

This genus is readily distinguished from Physarum by the columella, which gives origin to the capillitium; this feature indicates a relationship to Didymium and to Lamproderma.

§1. EUCYTIS. Sporangium globose, the columella not reaching its center.

1. CYTIDIUM PULCHERRIMUM, B. & R. Sporangium globose, stipitate; the wall a thin lilac-tinted membrane, with a dense closely adherent layer of granules of lime, dark purple or wine-colored. Stipe long, erect, dark purple to purplish black, tapering upward and entering the sporangium as a slight obtuse columella. Capillitium of slender lilac tinted threads, forming a dense net-work of very small meshes, with slight expansion at the angles; the nodules of lime very small, numerous, dark purplish or vinose in color, ellipsoidal or obtusely angular. Spores globose, even, lilac, 7-9 mic. in diameter.

Growing on old wood. Sporangium .4-.5 mm. in diameter, the stipe two or three times as long; the lime-nodules about the size of the spores. The purple stain, which the sporangia leave on white paper, is made by the granules of lime; the spores color the paper violet. Physarum pulcherrimum B. & Rav., and P. atrorubrum Peck.

2. CYTIDIUM CITRINUM, Schum. Sporangium globose, the base slightly flattened or umbilicate, stipitate; the wall a thin membrane, covered with small scales of lime, yellow or greenish-yellow, breaking up and falling away at maturity. Stipe stout, erect, yellow, longitudinally rugulose, expanded at the base, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium of slender tubules, forming a dense net-work, with slight expansions at the angles; the lime-nodules numerous, roundish or ellipsoidal, variable in size, yellow. Spores globose, nearly smooth, violaceous, 7-8 mic. in diameter.

Growing on bark, leaves, mosses, etc. Sporangium .5-.6 mm. in diameter, the stipe from once to twice this length. This, the typical species, I have not seen in this country, but forms with the sporangium lemon-yellow and grayish-yellow, with the stipe golden-yellow, connect it with C. rufipes. It is Physarum citrinum Schum. Diderma citrinum of Fries., S. M.

3. CYTIDIUM RUFIPES, A. & S. Sporangium globose, sometimes a little depressed and the base umbilicate, stipitate; the wall a thin membrane, covered with small scales of lime, golden-yellow to orange in color, breaking up at maturity and falling away. Stipe variable in length, slender, from orange or orange-red to dark red in color, sometimes blackish below, rising from a thin hypothallus, tapering upward and entering the sporangium as a short obtuse columella. Capillitium of slender tubules, forming a dense net-work of very small meshes, slightly expanded at the angles; the nodules of lime small, numerous, ellipsoidal or obtusely angular, orange to red in color. Spores globose, nearly smooth, violaceous, 8-10 mic. in diameter.

Growing on old wood, mosses, etc. A very abundant species. Sporangium .5-.7 mm. in diameter, the stipe from once to twice as long. As here defined, the species includes Physarum aurantium var. rufipes A. & S., and Physarum aureum var. chrysopus Lev, which I am unable to keep separate; the variation in size of the spores is not in correspondence with the variations in color of the sporangia. Physarum pulchripes Peck, and Physarum petersii B. & C., mostly belong here. The bright orange colors become dull or tawny with age and exposure to the weather.

4. CYTIDIUM RAVENELII, B. & C. Sporangium globose, stipitate; the wall a thin pellucid membrane, covered with small scales of lime, from gray or drab to pale umber in color, breaking up at maturity and falling away. Stipe variable in length, concolorous with the sporangium or darker below, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium of tubules, forming a dense net-work of very small meshes, with slight expansions at the angles; the lime-nodules small, numerous, ellipsoidal or obtusely angular, gray or drab to pale umber in color. Spores globose, nearly even, pale violaceous, 7-9 mic. in diameter.

Growing on old wood, mosses, etc. Sporangium about .5 mm. in diameter, the stipe once to twice this length. The species as here described includes Didymium ravenelii B. & C., Physarum simile Rost., and Physarum murinum Lister.

5. CYTIDIUM GLOBULIFERUM, Bull. Sporangium globose, the base sometimes flattened or slightly umbilicate, stipitate; the wall a thin, pellucid membrane, covered with small scales of lime, white, cream-colored, or sometimes pinkish, breaking up and falling away at maturity. Stipe variable in length, white or smoky-white, usually darker below, rising from a thin hypothallus, tapering upward and entering the sporangium as a short obtuse or conical columella. Capillitium of slender tubules, forming a dense, persistent net-work of very small meshes, more or less expanded at the angles; the nodules of lime variable in size, numerous, white, roundish, ellipsoidal or obtusely angular. Spores globose, nearly even, pale violaceous, 7-9 mic. in diameter.

Growing on old wood, bark, mosses, etc. A very common and abundant species. Sporangium .5-.6 mm. in diameter, the stipe from once to two or three times this length. The lime nodules in the capillitium are sometimes round and quite minute, then again they are large and obtusely angular; the columella varies from very short and conical to longer and more cylindric. Diderma globuliferum of Fries S. M., Physarum albicans Peck. The specimens with the columella well nigh obsolete, may be Tilmadoche columbina Rost.

6. CYTIDIUM MELLEUM, B. & Br. Sporangium globose, stipitate or subsessile; the wall a thin yellowish membrane, rugulose, covered by large irregular scales of lime, honey-color to golden-yellow, breaking up irregularly. Stipe short, sometimes very short or nearly obsolete, snow-white, expanding at the base into a small white hypothallus, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium a loose net-work of delicate tubules with broad vesicular expansions containing much lime; the nodules numerous, white or sometimes yellow, large, irregular, lobed, and branched. Spores globose, nearly even, pale violaceous, 7-9 mic. in diameter.

Growing on old leaves, sticks, herbaceous stems, etc.; not uncommon in this region. Sporangium .4-.5 mm. in diameter, the stipe about the same length or much shorter. Didymium melleum B. & Br. Didymium chrysopeplum B. & C. also belongs here and not with C. citrinum.

§2. REXIELLA. Sporangium ellipsoidal or pyriform, the columella prolonged nearly to the apex of the sporangium.

7. CYTIDIUM PENETRALE, Rex. Sporangium ellipsoidal or pyriform, stipitate; the wall a thin pellucid membrane, covered with small scales of lime, yellow-gray to greenish-yellow, rupturing at maturity into two to four segments. Stipe long, slender, translucent, pale red to dark red in color, tapering upward, entering the sporangium and prolonged nearly to the apex as a slender columella. Capillitium of very slender tubules, radiating from numerous points of the columella, forming a delicate net-work of very small meshes, scarcely expanded at the angles; the nodules of lime small, not numerous, roundish or obtusely angled, white or yellowish. Spores globose, very minutely warted, pale violaceous, 5.5-6.5 mic. in diameter.

Growing on old wood. A rare and singular species. Sporangium .5-.7 mm. in height by .3-.5 mm. in diameter, the stipe two or three times the height of the sporangium. There is an affinity between this species and the Physarella. The obscure Tilmadoche hians Rost., may be the same as the present species.

EXPLANATION OF PLATE XIII.

Fig. 49.--Angioridium sinuosum, Bull. a. Plasmodiocarp × 5 b. Capillitium and spores × 500.

Fig. 50.--Cienkowskia reticulata, A. & S. a. Plasmodiocarp × 5. b. Piece of plasmodiocarp × 90. c. Capillitium and spores × 500.

Fig. 51. Leocarpus fragilis, Dicks, a. Sporangia × 5. b. Capillitium and spores × 500.

Fig. 52.--Leocarpus caespitosus, Schw. a. Sporangia × 5. b. Capillitium and spores × 500.

Fig. 53.--Physarella oblonga, B. & C. a. Sporangia × 5. b. Sporangia × 90. c. Capillitium and spores × 500.

Fig 54--Cytidium penetrale, Rex. a. Sporangia × 5 b. Sporangia and columella × 90. c. Capillitium and spores × 500.

Fig. 55.--Cytidium globuliferum, Bull. a. Sporangia × 5. b. Sporangia × 90. c. Columella × 90 d. Capillitium and spores × 500.

VOL. XIX. PLATE XIII.

MORGAN ON MYXOMYCETES]