Lion Shield

Lion Shield (Pluteus leoninus) is the best known of the yellow-capped shield mushrooms, its epithet drawn from the tawny golden colour of a lion's coat. It is a small to medium species of decaying hardwood, slender in build, and it stands out on a dark log as a clean spot of chrome or honey yellow.

Within Pluteus it belongs to the group of thin-fleshed, brightly pigmented species whose cap cuticle is made of rounded or club-shaped cells rather than the long fibrillose hyphae of the Deer Shield group. That cellular structure is why the cap looks velvety or minutely granular over the centre and lacks the streaked radial fibrils of P. cervinus.

Modern work has shown that several closely similar yellow shields have long been lumped under this name, so collections vary in the exact shade of yellow, the degree of central wrinkling and the tint of the gill edge; the classic form is a golden-tawny cap with a velvety, sometimes finely veined disc and a translucent-striate margin.

Cap

The cap is 2–6 cm across, at first convex or bluntly conical and then flattening, sometimes with a low umbo. Colour is a bright golden yellow to tawny or honey-brown, usually deepest and slightly browner over the centre and paler towards the edge. The disc is dry, velvety and often minutely wrinkled or veined; the outer part is smoother and becomes translucent-striate when moist, showing the gills through the thin flesh.

Gills

The gills are free, close, broad and ventricose, white or pale yellowish when young and turning distinctly salmon-pink at maturity. In many collections the gill edges carry a faint yellowish tinge, best seen with a lens on fresh material.

Stipe

The stipe is 3–8 cm tall and 3–7 mm thick, slender and cylindrical, sometimes slightly swollen at the base. It is white to pale cream, often washed with yellow towards the base, smooth to finely fibrillose, occasionally with faint brownish longitudinal fibres. No ring and no volva are present.

Flesh and spore print

The flesh is thin, whitish to pale yellow, and unchanging when cut. The spore print is pink to salmon-pink; spores are smooth and broadly ellipsoid to subglobose. Pleurocystidia are thin-walled and lack apical hooks, distinguishing the group microscopically from P. cervinus.

Lion Shield grows on decaying hardwood: fallen trunks, stumps, large branches lying in leaf litter, and buried woody debris. Beech, alder, birch, willow, oak and poplar are all recorded hosts, and the species is most frequent in damp, shaded deciduous woodland, particularly along stream banks and in humid valley bottoms where wood stays moist.

It fruits from early summer through autumn, usually as scattered single fruit bodies or in small groups rather than in clusters. Distribution covers temperate Europe, with records extending through northern Asia; a number of similar yellow shields occur in North America and are treated by many authors as distinct species within the same complex.

The species is saprotrophic, producing a white rot in dead hardwood. It tends to occupy wood that is already partly decayed and moisture-retentive, colonising the softened interior of logs and buried branch fragments rather than sound freshly fallen timber.

Because its flesh is thin and its fruit bodies short-lived, Lion Shield depends on humid conditions to complete spore release, which is why it appears most reliably after summer and autumn rain in sheltered woodland. Spores discharged from the free gills are dispersed on air currents, and the pink deposit can often be seen on the wood or foliage directly beneath a mature cap.

Flame Shield (Pluteus aurantiorugosus) is scarlet to deep orange when fresh and has a yellow-flushed stem base; only faded specimens approach the yellow of Lion Shield, and the cap wrinkling is coarser. Pluteus romellii (Goldleaf Shield) inverts the colour scheme with a brown cap over a bright chrome-yellow stipe. Pluteus admirabilis is smaller and more delicate with a yellower, more strongly striate margin.

Away from the genus, small yellow Gymnopilus and Pholiota species on wood have gills attached to the stipe and rusty-brown spore prints, while yellow Hygrocybe waxcaps have thick waxy attached or decurrent gills, white spores and grow in grassland. Yellow Bolbitius species on dung and grass have a slimy, quickly collapsing cap and a rusty-brown deposit.