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.