SPORANGIA: sessile, crowded, polygonal from mutual pressure, flattened or somewhat convex, sometimes arranged in chains, 0.3 to 1.5 mm. diam., red-brown, purple-brown, nearly black, or gray from the presence of superficial crystals of lime, dehiscing in a circumscissile manner, indicated by a narrow, yellow area along the line of dehiscence

PERIDIUM: lower part of the sporangial wall firm, persistent as a shallow base; wall consisting of two layers, the outer charged with brown, granular matter, often intermixed with crystals of lime, and contracting in the upper part of the sporangium at maturity, separating and curling away from the membranous inner layer, which encloses the spores and may persist for some time; the two layers often curl away together as a lid.

CAPILLITIUM: an abundant web of slender, branched, yellow threads 1.5-2.5 µm diami., minutely warted or marked with regular close-set constrictions at intervals of 0.5-1 µm, and with irregular expansions.