Sporangia on the spines of fallen chestnut burs, scattered, pale yellow or whitish, small, globose, the peridium early evanescent above, more persistent below, stipitate; stipe small, tapering upward, from a small hypothallus; capillitium a dense but not expanding network attached chiefly to the lower portion of the sporangial wall, minutely waited or roughened, with few expansions or inflations; spores in mass pale yellow, under the lens colorless, almost smooth, 7–8 µ.

This singular little species is remarkable chiefly in the habitat it affects,—fallen chestnut burs. On these almost universal, but on nothing else, except on the fallen catkins of the same species. Regarded by Mr. Lister as A. cinerea, from which it differs constantly in form, in capillitium more open and with larger threads, 4–5 µ in diameter as well as in its unique habitat, and yellowish color.

Distribution coterminous with that of Castanea dentata Borkhausen,—eastern half of the United States.

2. Lachnobolus occidentalis Macbr.

[Plate II]., Figs. 2, 2 a, 2 b; 4 and 4 a.

Sporangia scattered or crowded upon a hypothallus more or less distinct, globose or ellipsoidal, short-stipitate, varying somewhat in color, at first rosy or flesh-colored, later brownish or ochraceous; the peridium exceedingly thin, pellucid, mealy, evanescent above, persisting as a shallow cup below; capillitium inelastic, rather closely netted of threads variable in thickness, marked by frequent thickenings or expansions, everywhere warted, attached to the peridial walls, spores in mass flesh-colored, under the lens colorless, smooth, globose, 7.5–9 µ.

This delicate and elegant little species appears to be not uncommon, but is probably generally passed over as an Arcyria, which it superficially resembles. When newly formed, the sporangia have a peculiar rosy or flesh-colored metallic tint, which is all their own. Within a short time this color passes, and most of the material comes from the field brownish or ochraceous in color. Typical sporangia are spherical on distinct short stipes; when crowded, the shape is of course less definite. The capillitium never expands as in Arcyria, but, exposed by the vanishing upper wall, remains a spherical mass resting upon the shallow cup-like base of the peridium.

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.