The
apothecia of
Helvella costifera are regularly stalked cup-shaped fruiting bodies (stipitate-cupulate), measuring 1.5–4 cm across and 1–4 cm tall. The inner spore-bearing surface, or
hymenium, appears greyish when fresh and dries to a dark greyish-brown. Externally, the cup (receptacle) is slightly downy (subpubescent) and matches the hymenium’s colour in fresh specimens, later becoming pale greyish-brown on drying. A distinct, hollow
stipe supports the cup and bears five to six prominent, blunt-edged ribs of yellowish-white that extend onto the underside of the cup. These ribs branch into two forks (dichotomously) near the apex without interconnecting and remain whitish even in dried specimens. Under the microscope, the outer tissue layer (excipulum) consists of prism-shaped to angular cells, with the outermost cell walls lightly pigmented brown. The spore-bearing
asci are pleurorhynchous—arising from a hook-shaped basal cell (
crozier)—and measure 230–270 × 12–15
μm, each enclosing eight
spores. The
ascospores are broadly
ellipsoid, 14.2–16.6 × 10.6–13.6 μm, smooth and transparent. Interspersed among the asci are sterile supportive filaments called
paraphyses, which are straight,
septate and 2.0–3.2 μm wide at the base, gradually swelling to about 4.5 μm at their tips. ==Distribution==