Chapter IV: OLIGONEMA, Rost. Sporangia subglobose, more or less irregular,

sessile and closely crowded, often in heaps, one upon another, the wall thin, smooth and shining; hypothallus none. Capillitium scanty, composed of elaters habitually irregular and abnormal, intermingled with the spores; elaters simple or sometimes branched, commonly very short, but varying greatly in length, even in the same sporangium; the surface marked with faint spirals, with a few annular ridges, minutely punctulate or altogether smooth. Spores globose, yellow.

The species of this genus are to be regarded as degenerate Trichias. Of course, the abnormality is exhibited most markedly by the elaters; nevertheless, the sporangia of some of the species have a peculiar habit of heaping themselves upon each other.

_A. Surface of the spores reticulate._

_a. Elaters with projecting rings._

1. OLIGONEMA NITENS, Lib. Sporangia subglobose, irregular, sessile, closely crowded and heaped upon each other, the wall thin, yellow, smooth and shining. Mass of capillitium and spores yellow; elaters simple or sometimes branched, 3-4 mic. in thickness, with a few distant projecting rings, the surface smooth between, or with very faint spirals, the extremities obtuse, or sometimes with a minute apiculus. Spores angularly or irregularly globose, the surface reticulate, 11-14 mic. in diameter.

Growing in small patches on and within rotten wood. Sporangia .4-.5 mm. in diameter; the elaters variable, some with as many as a dozen projecting rings, some with but a few or nearly smooth. _Trichia nitens_, Libert.

2. OLIGONEMA PUSILLA, Schr. Sporangia subglobose, irregular, sessile, scattered or collected together in heaps; the wall thin, yellow, smooth and shining. Mass of capillitium and spores yellow; elaters simple or sometimes branched, 4 mic. in thickness, sometimes with thicker inflated portions, the surface marked with low faint spirals or perfectly smooth; the extremities rounded and usually terminating in a smooth point, 3-5 mic. in length--this point either curved, bent to one side or turned back, and twisted around the extremity as a ring. Spores angularly or irregularly globose, the surface reticulate, 11-14 mic. in diameter.

Growing in small clusters in rotten wood. Sporangia .3-.5 mm. in diameter; the elaters variable in length, scarcely exceeding 100 mic. and often much shorter. _Trichia pusilla_, Schroeter.

_b. Elaters with no projecting rings._

3. OLIGONEMA FLAVIDUM, Peck. Sporangia obovoid to oblong, sessile, closely crowded and irregular from mutual pressure; the wall thin, yellow, shining, punctulate or minutely granulose. Mass of spores and capillitium yellow; elaters simple or sometimes branched, 3-4 mic. in thickness, sometimes with thicker inflated portions; the surface punctulate or minutely warted, occasionally marked with very faint spirals; the extremities usually rounded and obtuse, sometimes acute, and rarely with a minute apiculus. Spores angularly or irregularly globose, the surface reticulate, 11-14 mic. in diameter. See Plate I, Fig. 24.

Growing in dense patches on old wood and mosses. Sporangia .4-.6 mm. in diameter, and reaching 1 mm. in height, the elaters usually rather long, sometimes quite long and branched.

4. OLIGONEMA BREVIFILA, Peck. Sporangia subglobose, irregular, sessile, crowded, forming clusters or effused patches; the wall thin, yellow, densely granulose and venulose. Mass of capillitium and spores ochre-yellow; elaters simple or sometimes branched, often very short and fusiform, when elongated having long tapering extremities, sometimes with irregular swollen portions; the surface minutely granulose and rugulose, here and there a few spinules, occasionally with indistinct spirals. Spores angularly or irregularly globose, the surface reticulate, 11-12 mic. in diameter.

Growing on old wood and mosses. Sporangia .4-.5 mic. in diameter, the elaters varying greatly in length, some not more than 20 or 30 mic. long, others more than 100 mic. in length.

_B. Spores minutely warted._

5. OLIGONEMA FULVUM, Morgan n. sp. Sporangia rather large, subglobose, sessile, closely crowded and more or less irregular; the wall tawny yellow, very thin and fragile, smooth, shining and iridescent. Mass of capillitium and spores tawny yellow; elaters simple or sometimes branched, mostly very short, 4 mic. in thickness, sometimes with thicker swollen portions; the surface marked with low smooth spirals, in places faint and obsolete; the extremities rounded and obtuse, usually with a very minute apiculus, 1-3 mic. in length. Spores globose, minutely warted, 10-13 mic. in diameter.

Growing on an old effused Sphæria. Sporangia .6-.8 mm. in diameter, the elaters mostly 40-80 mic. in length, rarely much longer and sometimes shorter; the longer elaters and those that are branched often arise from confluence of the shorter ones.

EXPLANATION OF PLATE I.

Fig. 13.--Perichæna depressa, Lib.

Fig. 14.--Ophiotheca Wrightii, B. & C.

Fig. 15.--Lachnobolus globosus, Schw.

Fig. 16.--Arcyria Cookei, Massee.

Fig. 17.--Arcyria minor, Schw.

Fig. 18.--Heterotrichia Gabriellæ, Massee. (After Massee.)

Fig. 19.--Hemiarcyria plumosa, Morgan.

Fig. 20.--Hemiarcyria funalis, Morgan.

Fig. 21.--Calonema aureum, Morgan.

Fig. 22.--Trichia fallax, Pers.

Fig. 23.--Trichia scabra, Rost.

Fig. 24.--Oligonema flavidum, Peck.

NOTE.--Each figure exhibits the sporangium as it appears magnified about 100 diameters, and the capillitium and spores magnified about 500 diameters.

VOL. XVI. PLATE I.]

* * * * *

THE MYXOMYCETES OF THE MIAMI VALLEY, OHIO.

BY A. P. MORGAN.

Third Paper.

(Read February 6, 1894.)

ORDER VI. STEMONITACEÆ.

Sporangia globose or ovoid to oblong and cylindrical, stipitate; the wall very thin and fragile, soon disappearing. Stipe tapering upward and continued within the sporangium as a more or less elongated columella. Capillitium of slender brown threads, arising from numerous points of the columella, repeatedly branching and usually anastomosing to form a network, persistent and rigidly preserving the outline of the sporangium. Spores globose, brown or violaceous.

This order is readily distinguished by the brown persistent capillitium, arising from a lengthened columella, and rigidly maintaining the form of the sporangium.

Table of Genera of Stemonitaceæ.

_A. Stipe and columella brown or black._

_a. The columella scarcely reaching the center of the sporangium._

1. CLASTODERMA. Threads of the capillitium forking several times, but not combined into a network.

2. LAMPRODERMA. Threads of the capillitium branching and anastomosing to form a network.

_b. The columella extending beyond the center of the sporangium._

3. COMATRICHA. Threads of the capillitium forming only an interior network, attaining the wall by numerous more or less elongated free extremities.

4. STEMONITIS. Threads of the capillitium forming an interior network of large meshes and a superficial network of smaller meshes.

5. ENERTHENEMA. Threads of the capillitium pendent from a discoid membrane at the apex of the columella.

_B. Stipe and columella white or yellowish._

6. DIACHAEA. Threads of the capillitium branching and anastomosing to form a network.