About Phellodon niger (Fr.) P.Karst.
Phellodon niger (Fr.) P.Karst. produces fruitbodies with both a cap and a stipe, placing it in the group of stipitate hydnoid fungi. Individual caps grow up to 5 cm (2.0 in) in diameter, but neighboring fruitbodies often fuse their caps to form larger compound growths. Caps range from flat to depressed to somewhat funnel-shaped; they start with a felt-like texture, and later develop concentric pits, wrinkles, and ridges. Caps are initially whitish, sometimes with purplish tints, and later darken to grey, grey-brown, or black in the center. The stipe grows up to 4 cm (1.6 in) long, and is roughly the same color as the cap. Grey spines up to 4 mm long grow on the underside of the caps. The outer layer of the stipe is a thick, felty mycelium layer that absorbs water like a sponge. In high humidity conditions, actively growing P. niger caps can form noticeable drops of black liquid. When dried, the flesh has an odor of fenugreek. Mushroom tissue turns bluish-green when tested with a potassium hydroxide solution. The spores are ellipsoid and hyaline (translucent), measuring 3.5–5 by 3–4 μm. Spore-bearing basidia are club-shaped, four-spored, and measure 25–40 by 5–7 μm. Phellodon niger has a monomitic hyphal system, and produces generative hyphae with a diameter of 2.5–5 μm. This species is classified as inedible. Phellodon niger forms ectomycorrhizae with Norway spruce (Picea abies), and this association has been comprehensively described. Its ectomycorrhizae can be distinguished from those of other Thelephorales species by the unique shape of its chlamydospores. Stable isotope ratio analysis of carbon-13 abundance shows P. niger has a metabolic signature similar to that of saprotrophic fungi, which suggests it may be able to get carbon from sources other than a tree host. Phellodon niger has a widespread distribution across continental Europe, and is also found in North America. In a preliminary assessment for a red list of threatened British fungi, P. niger is considered rare. In Switzerland, it is classified as a vulnerable species. Phellodon niger was included in a Scottish study focused on developing species-specific PCR primers to detect stipitate hydnoid mycelia in soil. DNA testing of UK collections labelled as P. niger uncovered additional cryptic species. PCR analysis can detect the presence of a Phellodon species up to four years after fruitbodies have appeared, allowing more accurate assessment of their potential decline and extinction risk.
