The genus _Amaurochaete_ as defined by Rostafinski and the genus _Reticularia_ as represented by _R. lycoperdon_ Bull. stand, the expression, perhaps, of not dissimilar histories. Whether in regressive or progressive series, each to-day presents a case of arrested development. Each in aethalioid fructification, reveals a mass of involved individual (?) sporangia, so imperfectly developed that their outlines can be inferred rather than anywhere, with absolute definiteness, certainly ascertained. Perhaps, because similar sporangia in the group to which either belongs, do come under other circumstances, to more perfect individual form and function--perhaps for this reason we may look upon these aethalia as exhibiting a suspended performance; the sporangia have failed to go forward to what was evidently a possible, though apparently not an essential destiny in form and figure. For the care and dispersal of the spores, achievement must surely be somewhat impaired. Whatever the measure of such inefficiency, among the _Stemonitales Amaurochaete_ shows the acme, as _Reticularia_ among the brown-spored forms. In _Amaurochaete_ the individuality of anything like separate sporangia is less clear. The view afforded, however, by a good vertical section of a well-developed colony or cushion is interestingly arborescent. Ragged, dendroid stems arise, dissipated above into a network most intricate, a "pleached arbor" if you please. The resemblance of the overhead net to that presented by a stemonitis or comatricha is very striking. =Key to the Species of Amaurochaete= _A._ Capillitium rigid, irregular spores rough 1. _A. fuliginosa_ _B._ Capillitium soft, woolly, cincinnate, spores as in _A_ 2. _A. tubulina_ 1. AMAUROCHAETE FULIGINOSA (_Sowerby_) _Macbr._ PLATE V., Figs. 8, 8 _a_. 1803. _Lycoperdon fuliginosum_ Sow., _Eng. Fung._, t. 257. 1805. _Lycogala atrum_, Alb. & Schw., _Consp. Fung._, p. 83. 1875. _Amaurochaete atra_ (Alb. & Schw.) Rost., _Mon._, p. 211. Fructification aethalioid, varying in form and size, if on the upper side of the substratum, pulvinate, if below pendent and almost stipitate, covered with a delicate cortex, at first shining, soon dull, black, fragile, and early dissipated; hypothallus long-persisting, supporting the capillitium, which is extremely variable, irregular, and for its perfection dependent upon the form assumed by the aethalium, and the conditions of weather, etc., under which it matures, sometimes, especially when prostrate, in a very much depressed aethalium, spreading into long fibrous threads, again under better conditions rising in columella-like forms, supporting a peripheral net; spores dark brown or black, irregularly globose, spinulose, 12.5-15 mu. Common in Europe, and probably not uncommon in this country wherever pine forests occur. Specimens before us are from New England and New York, Ohio, Carolina, Colorado. Canada.