Puff-balls of considerable size, growing in the sandy soil of dry regions. A very distinct genus, in no way related to Scleroderma, and resembling it only in its thick, corky, inner peridium. The threads of the capillitium originate within the tissue of the gleba, along with the spores, and are set free by deliquescence, the same as in Bovista. Morgan.
M. spinulo´sum Pk. Peridium globose, depressed globose, sometimes elongated and often irregular, with a thick, cord-like root. Cortex at first a thickish, white, smooth, continuous layer; after maturity it cracks or becomes furrowed into large polygonal areas, and at length falls away in large flakes or scales; inner peridium very thick, at first white and coriaceous, becoming hard, dry, brown and rigid, the upper part finally breaking up into irregular lobes or fragments. Mass of spores and capillitium compact then friable, at first olivaceous, then dark purplish-brown; the threads bent, curved and flexuous, subhyaline, .2-.7 mm. in length, about the same thickness as the spores, with a few short branches, and with scattered prickles, which are most abundant toward the acute extremities. Spores globose, very minutely warted, opaque, 9–12µ in. diameter, often with a minute or slender hyaline pedicel.
Growing on the sandy soil of the western prairies. Wisconsin, Brown; Dakota, Ellis; Nebraska, Webber; Colorado, Trelease; Kansas, Kellerman, Cragin; New Mexico, Irish.
Peridium 2–4 in. in diameter. The plants are said to grow together in groups, sometimes of many individuals; after maturity they are easily loosened from their place of growth and are then rolled about by the wind. Morgan.
No report upon edibility. Probably good.
FAMILY III.—SCLERODERMA´CEÆ.
Peridium discrete from the gleba, often with a columella; cells of the gleba subpersistent. Morgan.
GENUS I.—SCLERODER´MA Pers.
Scleros, hard; derma, skin.
Skin firm with an innate bark, bursting irregularly; woolly threads adhering on all sides to the bark and forming distinct veins in the central mass. Base sterile, usually becoming elongated into a stem-like structure. Spores large, granulated.