Primordium formation in Hydropus subalpinus (Tricholomatales, Basidiomycetes)

Hydropus subalpinus is exocarpic amphiblemate. The pubescence of the stipe is a cauloblema that sometimes forms a spurious partial veil in young primordia. The pileoblema becomes a gelatinised pileipellis with a few more or less erect cells on the pileus and a few layers of periclinal physalohyphae on the pileus margin. The stipe and pileus contexts are sarcodimitic, and the morphogenetic function of the physalohyphae during the expansion of the stipe and the pileus is discussed, based on specimens with an aborted sarcodimitic structure. The carpogenesis of Hydropus subalpinus is similar to that of Hydropus anthidepas and Baeospora myosura.