This species has been in the United States generally distributed as _L. incarnatus_ (Alb. & Schw.) Schroet. A careful study of all descriptions of European forms and comparison of many specimens leads us to believe that we have here to do with a type presenting constant peculiarities. We have in America nothing to correspond with the figures of Schweinitz, Berkeley, or Lister. In the American gatherings the sporangia are uniformly regular, globose, very generally short-stipitate, more or less closely gregarious, never superimposed, or heaped as shown in Berkeley's figure, for instance, _Ann. and Mag. Nat. Hist._, IV., xvii., Pl. ix., Fig. 2. The plasmodium of our species is white; as it approaches maturity a rosy metallic tinge supervenes, quickly changing to dull yellow or alutaceous. The graphic description given by Fries of _Perichaena incarnata_, _Syst. Myc._, III., p. 193, presents scarcely a character attributable to the form before us. _L. congesta_ Berk. & Br., evidently the form figured and described by Lister, _Mycetozoa_, p. 194, Pl. lxx., B., resembles our species in color and capillitium, but is entirely different in habit. Not uncommon. Maine, Iowa, Missouri, Nebraska. =2. Arcyria= (_Hill_) _Pers._ 1751. _Arcyria_ Sir John Hill, _Gen. Nat. Hist._, II., p. 47. 1801. _Arcyria_ Pers., _Syn. Fung._, p. 182. Sporangia ovoid or cylindric or even globose, stipitate; the peridium thin, evanescent to near the base, the lower part persisting as a calyculus; the stipe variable, packed with free cell-like vesicles, resembling spores, but larger; capillitium attached below, to the interior of the stipe or to the calyculus, in form an elastic network, the tubules adorned with warts, spinules, half-rings, etc., but without spiral bands or free extremities. Micheli, of course, discovered the arcyrias, put them in two genera and several species, which we may only dimly recognize. Persoon first saw distinctly the outlines of the genus as now understood and adopted the name given by Hill in his curiously prolix description of certain species, probably partly of the genus _Arcyria_, partly _Stemonitis_. =Key to the Species of Arcyria= _A._ Mature capillitium loosely adhering to the calyculus. _a._ Mature capillitium far-expanded, drooping. i. Dusky. O Long, 12 mm. or more 1. _A. magna_ OO Shorter, about 6 mm. 2. _A. oerstedtii_ ii. Yellow 3. _A. nutans_ _b._ Mature capillitium short, not drooping, though sometimes procumbent. i. Capillitium greenish yellow 4. _A. versicolor_ ii. Capillitium reddish, flesh-colored, at length sordid, etc. O Capillitium marked by transverse half-rings, cogs, etc. 5. _A. incarnata_