Silky Parchment Identification Guide

The first impression

This is a fungus you find by looking down at dead twigs rather than out across the forest floor. You will be in an eastern hardwood wood, often in a damp bottomland or a shaded slope with musclewood and hop hornbeam in the understorey, and the fungus appears as rows of small, pale, shell-shaped brackets running along a dead attached branch or a fallen limb no thicker than a wrist. Individually they are tiny - the size of a thumbnail - but they occur in numbers, fused edge to edge into wavy ribbons, stacked in tiers, and sometimes curling into rosettes where several have grown together. The colour is a soft white to greyish buff and the upper surface has a silky sheen, so a well-colonised branch looks as though it has been trimmed with pale ruffled ribbon.

The fruit body form

Structurally this is a crust fungus that has lifted its edge away from the wood. Most of the colony is effused-reflexed: a thin sheet spread over the bark with the outer part turned outward and upward into a narrow bracket. Individual caps are 5-25 mm wide and project only a few millimetres to about 1 cm from the wood, fan-shaped, shell-shaped or semicircular, and very thin - often well under a millimetre through the flesh. The margin is thin, sharp, frequently wavy or lobed, and curls inward as the fruit body dries. When wet the whole structure is pliant and leathery and can be bent double; when dry it becomes stiff and brittle and snaps. It revives repeatedly with rain, which is why colonies persist on the same branch for a year or more.

Reading the upper surface

This is where the species earns its name. The upper surface is finely silky-tomentose, covered in short appressed hairs that catch the light, and it is distinctly radially striate: fine lines run outward from the attachment to the margin, giving the surface a combed or grained appearance under a lens. Colour is white to cream, ageing to pale buff, greyish or faintly ochre, and there is usually a suggestion of concentric zoning - faint, low-contrast bands of slightly different tone rather than the bold multicoloured banding of some relatives. Weathered old specimens often go grey-green where algae colonise them, which can be misleading; look for a fresh growing margin at the edge of the colony to judge the true colour.

The spore-bearing surface

Turn the branch or bend a bracket back. The underside is the hymenium, and it is completely smooth - no gills, no pores, no teeth, no wrinkles beyond a slight unevenness near the point of attachment. It is pale: whitish, cream, buff or a pale tan, sometimes marginally darker or more ochre than the upper surface, and it dulls with age. A smooth undersurface is what defines this genus and is the first thing to establish, because it eliminates the polypores and the split-gill fungi that share exactly the same dead branches.

Flesh and colour change

The flesh is extremely thin, whitish, and tough-leathery when moist. Section a bracket with a razor and you will see essentially a single pale layer with the hairy upper skin above it; there is no distinct black line, no gelatinous band and no zoned interior. Now run the critical test for this genus: scratch or cut the fresh, moist hymenium with a fingernail or blade and watch for a minute. The Silky Parchment does not bleed - no red, orange or brownish juice appears at the wound, and the surface simply stays pale. Several closely similar crusts exude a red liquid when scratched, so this negative result is a decisive, repeatable field character. Do it on a well-hydrated specimen, because dry fruit bodies of the bleeding species will not react either.

Getting a spore deposit

A print is possible with a little patience. Cut a section of branch carrying fresh brackets, position it so the hymenium faces down over a piece of black card, and enclose the whole thing in a box or bag with a damp paper towel to keep the humidity up. Left overnight, a fresh colony will deposit a thin white print, sometimes so sparse it reads only as a faint bloom against the black. Under a microscope the spores are small, smooth, thin-walled and cylindric to narrowly ellipsoid, and they are amyloid, turning blue-grey in Melzer's reagent. The hymenium also contains pointed sterile cells that are visible in a squash mount.

Substrate, ecology and season

This species is a saprotroph of dead hardwood, and it shows a strong preference for smaller-diameter wood: dead attached branches still on the tree, recently fallen limbs, and slender fallen stems. In eastern North America it is most consistently associated with American hornbeam or musclewood and with hop hornbeam, though it turns up on oak, maple, beech and other broadleaves. It colonises the branch under the bark and fruits along the wood as the bark loosens and falls away, decaying the wood as it goes. Fruit bodies are effectively perennial in appearance - present all year, drying to stiff pale flakes in drought and reviving and resuming growth after rain - so unlike most gilled fungi there is no real season to wait for. Expect it in shaded, humid situations rather than in exposed sunny ones.

Separating the look-alikes

Stereum complicatum shares the small size and the branch habit but is warm orange to cinnamon on both surfaces, strongly curled, and is most typical on oak.

Stereum ostrea, the false turkey tail, is far larger, with caps several centimetres across banded in bold concentric zones of brown, tan, orange and buff, and a broader, more fan-like outline.

Stereum hirsutum has a coarsely hairy, shaggy upper surface in yellow-buff tones and a bright yellow to orange hymenium when fresh.

Stereum gausapatum and Stereum sanguinolentum are the bleeders: scratched fresh, their hymenium runs red, and their upper surfaces are browner and more woolly. Sanguinolentum is also a conifer species.

Chondrostereum purpureum is smooth beneath like a Stereum but its hymenium is a distinct purple to lilac-brown.

Xylobolus frustulatus forms hard crusts cracked into small separate blocks on old oak.

Trametes and other polypores are ruled out instantly by their pored undersides, and Schizophyllum commune by its longitudinally split, gill-like folds and densely white-woolly cap.

Plicaturopsis crispa looks similar in size and colour from above but has strongly wrinkled, folded, vein-like ridges on the underside rather than a smooth surface.

Field checklist

Small thin fan-shaped brackets fused in rows on dead hardwood branches; upper surface silky and finely radially striate, white to buff with faint zoning; underside smooth and pale; leathery when wet, brittle when dry; no red juice when scratched; white spore print. That is Stereum striatum.