Geaster hygrometricus. Pers.
Water-Measuring Earth-Star.
Photo by C. G. Lloyd.
Figure 483.—Geaster hygrometricus. Natural size.
The unexpanded plant is nearly spherical. The mycelial layer is thin, tearing away as the plant expands, the bark or skin falling with the mycelium. The outer coat is deeply parted, the segments, acute at the apex, four to twenty; strongly hygrometric, becoming reflexed when the plant is moist, strongly incurved when the plant is dry. The inner coating is nearly spherical, thin, sessile, opening by simply a torn aperture. There is no columella. The threads are transparent, much branched, and interwoven. The spores are large, globose, and rough.
The plant ripens in the fall and the thick outer peridium divides into segments, the number varying from four to twenty. When the weather is wet the lining of the points of the segments become gelatinous and recurve, and the points rest upon the ground, holding the inner ball from the ground. In dry weather the soft gelatinous lining becomes hard and the segments curve in and clasp the inner ball. Hence its name, "hygrometricus," a measurer of moisture. The plant is quite general.