Helvella leucopus
Anamorph: not known.
Teleomorph: stromata absent. Ascomata discomycetous, stipitate. Cap (10-) 25-35 mm diam. and 17-40 mm high, saddle-shaped or mitre-like with two or three distinct irregular lobes. Hymenium brown-black to black (black when dry), sometimes with purple or chocolate brown tinges. Outer surface white to pale grey, glabrous. Ectal excipulum (outer surface layer) 85-150 µm thick, composed of chains of angular hyaline cells, the outermost cells cylindrical to clavate, 20-60 x 6-20 µm in size. Internal tissue (below the hymenium) 200-300 µm thick, composed of interwoven hyphae 3-6 µm diam., interspersed with thicker-walled hyphae 6-10 µm diam. Stipe 20-55 × 7-10 mm, generally squat, often expanded at the base (to 15-20 mm), round in section, sometimes slightly furrowed below, hollow, white, sometimes stained pale grey or brown with age, glabrous, which may be partly buried. Interascal tissue of unbranched paraphyses with swollen apices to 5-9 µm diam., containing a brown pigment. Asci 310-360 × 14-17 µm, cylindrical, fairly thick-walled, the apex rounded, operculate, 8-spored. Ascospores 20-24 × 13-15 (-16) µm, mean length/breadth ratio 1.5, ellipsoidal to broadly ellipsoidal, fairly thin-walled, hyaline, smooth, containing a large central lipid droplet surrounded by smaller ones, without a gelatinous sheath or appendages.
Not formally assessed, but considered as Vulnerable / B in the provisional Red Data List (Evans et al. 2006). In GB&I, only known from recent collections at two localities. One of these has been successfully resurveyed several times since its original discovery. The site is a NNR and designated as an SSSI so enjoys some degree of statutory protection.
Of other species of Helvella fruiting in spring, H. acetabulum has a strongly furrowed stipe, and H. corium is entirely blackish grey. Both have a cupulate rather than a saddle-shaped hymenium.
In GB&I, reported to be associated with species of the Populus alba group (identified as P. ? canescens or P. tremula) and Salix repens.
In GB&I, recorded from VC41 Glamorgan and VC44 Carmarthenshire. Widely distributed in central and southern Europe.
Found in sand dune habitats, in moss patches under/close to the woody plants listed above.