Rostafinski placed this genus near the _Didymieae_ on account of the calcareous columella and the non-calcareous capillitium. On the other hand the structure of the capillitium and the iridescent simple peridium ally _Diachaea_ to _Lamproderma_ and the _Stemoniteae_; the only distinction being the calcareous stem. It is simply an intermediate genus to be placed here more conveniently than anywhere else in what is of necessity a linear arrangement. =Key to the Species of Diachaea= _A._ Stipe and columella white. _a._ Sporangium cylindric 1. _D. leucopodia_ _b._ Sporangium globose. i. Evidently stalked 2. _D. splendens_ ii. Stalk very short, 5 mm., conic. O Spores warted 3. _D. bulbillosa_ OO Spores faintly netted 4. _D. subsessilis_ _B._ Stipe yellowish or orange 5. _D. thomasii_ 1. DIACHAEA LEUCOPODIA (_Bull._) _Rost._ 1791. _Trichia leucopodia_ Bull., _Champ. de la France_, Pl. 502, Fig. 2. 1825. _Diachaea elegans_ Fries, _Syst. Orb. Veg._, I., p. 143. 1875. _Diachaea leucopoda_ (Bull.) Rost., _Mon._, p. 190. Sporangia rather closely gregarious, metallic blue or purple iridescent, cylindric or ellipsoidal, obtuse, sub-umbilicate below, stipitate; stipe short, much less than one-half the total height, snow-white, tapering upward; hypothallus white, venulose, occurring from stipe to stipe to form an open network over the substratum; columella thick, cylindric, tapering, blunt, terminating below the apex, white; capillitium springing from every part of the columella, of slender threads, brown, flexuous, branching and anastomosing to form an intricate net; spores in mass nearly black, by transmitted light dull violaceous, minutely roughened, 7-9 mu. A very beautiful species; not uncommon in the eastern states; rare west of the Mississippi. Easily recognized, amid related forms, by its snow-white stem, a feature which did not escape the notice of Bulliard and suggested the accepted specific name. Fries adopted the specific name proposed by Trentepohl and wrote _D. elegans_, simply because to him the peridium was "admodum elegans." The peridium is exceedingly thin and early deciduous; the stipe long persistent. The plasmodium, dull white, was observed by Fries at the beginning of the century; "morphoseos clavem inter myxogastres hoc genus primum mihi subministravit." This species, as the diachaeas generally, affects fallen sticks and leaves in orchards and forests and even spreads boldly over the foliage and stems of living plants. New England, New York, Pennsylvania, Maryland, Virginia, South Carolina, Ohio, Iowa, California, Canada. 2. DIACHAEA SPLENDENS _Peck._ PLATE VII., Figs. 1, 1 _a_, 1 _b_, 1 _c_. 1877. _Diachaea splendens_ Peck, _Rep. N. Y. Mus._, XXX., p. 50.