Hymenoscyphus laetus

On a semi-submerged slender stem of Populus alba.

Medullary excipulum of textura intricata, with hyaline hyphae thin- to slightly thick-walled, densely interwoven.

Ectal excipulum of textura prismatica, with more elongated hyphae toward the outer part and containing yellowish refractive vacuoles.

Asci cylindric-clavate, 8-spored, inoperculate, with biseriate to irregular spore arrangement within the ascus, up to 200 µm long and 14 µm wide, with distinct croziers at their base and an amyloid apical apparatus.

Paraphyses filiform, cylindrical, septate, very slightly widened at the apex up to a maximum width of 3 µm, with abundant tiny vacuoles inside clearly visible in fresh material, not projecting above the level of the asci.

Ascospores ellipsoidal to subfusiform, smooth, hyaline, thin-walled, with abundant vacuolar internal content, inamyloid in IKI or Melzer's reagent.