This work describes the ultrastructural characters ofPsilocybe quebecensis
Ola'h &Heim, an hallucinogenic species, the so far known most northernGeophila exhibiting psychodysleptic action.
Samplings have been selected on three different parts of the carpophore. Tissues obtained from the gills, central part of the stipe and hyphae below the fruit body of freshly collected carpophores.
An accumulation of reserve polysaccharides has been localized in the hyphas of the sub-hymenium and in the mycelium around the stem. We give evidence that two types of pore septum characterise this species. The succession of the sporal tegument of dormant basidiospores and other ultrastructural characters are considered.