Sporangia distinct, gregarious, globose or depressed-globose, stipitate, cernuous; the peridium very delicate, evanescent, thickened on the inside by numerous meridional costae which are joined at frequent intervals by fine transverse threads more or less parallel to each other, forming a persistent network of rectangular meshes. The ribs or costae of the spore-case radiate from the top of the stipe and unite again at the top of the sporangium in a feeble, irregular net. Schrader, _Nov. Gen. Pl._, p. 11, 1797, applied the name _Dictydium_ to all _Cribraria_-like species in which the calyculus was wanting. Fries follows this, _Syst. Myc._, III., p. 164. Rostafinski, _Versuch_, p. 5, _Mon._, p. 229, first correctly limits the genus and separates it from _Cribraria_. 1873-75. A single species is widely distributed throughout the world,-- 1. DICTYDIUM CANCELLATUM (_Batsch_) _Macbr._ PLATE I., Figs. 6, 6 _a_ and PLATE XIX., Figs. 1, 1 _a_, 1 _b_, 1 _c_, 2, 3. 1789. _Mucor cancellatus_ Batsch, _Elench. Fung._, II., p. 131. 1797. _Dictydium umbilicatum_ Schrad., _Nov. Gen. Pl._, p. 11. 1801. _Cribraria cernua_ Pers., _Syn._, p. 189. 1816. _Dictydium cernuum_ Nees, _Syst. d. Pilz._, p. 117. 1875. _Dictydium cernuum_ (Pers.) Rost., _Mon._, p. 229. 1893. _Dictydium longipes_ Morg., _Cin. Soc. Jour._, p. 17, in part. Sporangia gregarious, depressed globose, nodding, the apex at length umbilicate, stipitate, in color brown, or brownish purple; the stipe varying much in length from two to ten times the diameter of the sporangium, attaining 5-6 mm., generally erect, more or less twisted and pallid at the apex, below dark brown, with hypothallus small or none; calyculus often wanting, when present a mere film connecting the ribs of the net; the net made up chiefly of meridional ribs connected at intervals by transverse parallel threads, above an open _Cribraria_-like network closing the apex and more or less rudimentary; the spores varying in color through all shades of brown and purple when seen in mass, by transmitted light reddish, 5-7 mu, smooth or nearly so.