_B._ Peridial thickenings in form of parallel meridional ribs connected by delicate transverse threads 2. DICTYDIUM =Cribraria= (_Pers_) _Schrader._ 1794. _Cribraria_ Persoon, Roemer, _N. Bot. Mag._, I., p. 91, in part. 1797. _Cribraria_ Schrader, _Nov. Gen. Plant._, p. 1, in part. 1875. _Cribraria_ Rostafinski, _Mon._, p. 229. Sporangia distinct, gregarious or closely crowded, globose or obovoid, stipitate; the stipe of very varying length; the peridium simple, marked within by distinct and peculiar, granular, thickenings, which below take the form of radiating ribs, supporting the persisting cup, _calyculus_, and above, by extremely delicate anastomosing branches, unite to weave a more or less regular net with open polygonal meshes; spores various, more often yellowish or ochraceous, sometimes brown, reddish, or purple. The genus _Cribraria_, as limited by Persoon, included all forms in which the peridium is thin, evanescent half-way down, or entirely, and in which capillitium, as Persoon regarded the case, is formed of a network of reticulate threads surrounding the spores. Schrader redefined the genus; opposed Persoon's view as to the capillitial nature of the net, and separated the genus _Dictydium_, but by imperfect limitations,--in fact, chiefly because of the more completely evanescent peridium. Fries follows Schrader. Rostafinski first clearly separated the two genera, and his classification is here adopted. Nevertheless, after reviewing the subject entire one is more and more inclined to appreciate the commendation of Fries; "Auctor Schrader, qui insuper plurimas species detexit, et hoc et sequens genus ita proposuit ut sequentes vix aliquid addere valuerint." As to the habitat of the cribrarias, the remark of Schrader is still pertinent--"in vetustissimis plenariae destructionis proximis arborum truncis"--for all the species. Rotten, coniferous wood seems to be preferred, but the decayed logs of trees of other orders are by no means refused. Rotten oak forms a very common habitat. =Key to the Species of Cribraria= _A._ Sporangia with spores ochraceous or brownish. _a._ Sporangia larger, .5 mm. or more. 1. Net poorly developed, sometimes merely indicated 1. _C. argillacea_ 2. Net conspicuous, nodes expanded, not swollen. i. Calyculus reticulately thickened, ill-defined above 2. _C. macrocarpa_ ii. Calyculus with radiant lines or ribs; net small-meshed; free ends none 6. _C. aurantiaca_ iii. Net wide-meshed, calyx rufous 4. _C. rufa_ iv. Calyx replaced by ribs 5. _C. splendens_ 3. Net conspicuous, nodules swollen. i. Net-threads simple; free ends many 7. _C. dictydioides_