Clavaria atroumbrina  

A black/dark club-like basidiomata 2-4 cm tall arising singly or in small clusters from grass and moss in temperate grasslands.

Basidiomata solitary or in small clusters of 2–3, unbranched, cylindrical, sometimes slightly clavate (club-shaped), subacute or obtuse, 20–40 mm tall, dark brown, rufous (redish-brown), yellowish or blackish brown, tips blackening with age. Fertile part 1–3 mm broad, sterile base indistinctly delimited, up to 1–2 mm broad, paler, yellowish brown, base white, finely cottony. Flesh elastic, without smell, taste mild. Reaction to FeCl₃ negative. Spores (5.0–)5.2–6.1(–6.3) × (2.8–)2.9–3.4(–3.5) μm, (average 5.6 × 3.2 μm), oblong, often phaseoliform (bean-shaped) or amygdaliform (almond-shaped) in side view, hyaline (translucent), thinwalled, smooth. Basidia clavate (club-shaped), 20.5–42.1(–49.8) × 5.4–6.5(–8.1) μm, clampless, tetrasporic (produced in groups of four), some with dark encrustations. Hymenium thickening, 50–80 μm deep, subhymenium pseudoparenchymatic (compact mass of tissue, made up of interwoven hyphae or filaments, that superficially resembles plant tissue), composed of intricate, densely interwoven hyphae, some with encrusted pigments, with cells measuring 20–30(–60) × 2–6 μm, not sharply delimited from trama (the loosely woven hyphal tissue in basidiomycetous fungi forming the central substance of the lamellae or other projections of the hymenophore). Trama composed of parallel or slightly interwoven, thinwalled, hyaline (translucent) hyphae, with cells 70–100 × 3.5–13 μm, some septa with intracellular pigments, and with few encrustations. Surface of the sterile base cutis, some of the hyphal terminations with ochraceous (light brownish yellow) intracellular pigments. Pigments dark, intracellular, present especially in basidia, also in hymenium and subhymenium. Clamp connections absent in all tissues.

Adapted from Kautmanová (2012). “European species of Clavaria (Agaricales, Agaricomycetes) with dark basidiomata–a morphological and molecular study.” Persoonia: Molecular Phylogeny and Evolution of Fungi 29: 133-145.