Helvella costifera

An uncommon spring species, very similar to Helvella acetabulum, characterized by its generally less cup-shaped apothecium, light grey color, and white anastomosing ribs extending almost to the cup margin.

Outer surface hyphae hair-like, cylindrical, hyaline, septate, with constrictions at the septa and swellings in the terminal cell.

Medullary excipulum hyphae filamentous, of textura intricata, hyaline; ectal excipulum hyphae globose, subglobose to slightly angular by mutual compression, hyaline and thin-walled.

Asci cylindrical, 8-spored, uniseriate, up to 300 µm long and up to 14 µm wide, inamyloid in Melzer's reagent.

Paraphyses filiform, simple, unbranched, very slightly swollen at the apex up to a maximum width of 5 µm, with faint granular internal content that darkens noticeably in Melzer's reagent.

Ascospores ellipsoidal, smooth, hyaline, moderately thick-walled, with a large oil or lipid droplet inside occupying almost the entire spore volume.