Gilled Bolete Identification Guide

A Mushroom That Contradicts Itself

You are walking an oak-lined trail on a humid summer morning, and a medium-small mushroom on a mossy bank catches your eye. The cap is dry, dull reddish-brown and finely velvety, exactly the surface you associate with a small bolete. You turn it over expecting a spongy pore layer and instead find thick, widely spaced, egg-yolk-yellow gills running down the stipe. That contradiction - bolete cap over blatant gills - is the entire experience of finding Phylloporus rhodoxanthus, and once you have felt it, the species is hard to forget.

The lesson worth carrying forward is that gills and pores are not two separate lineages. Phylloporus is a genuine member of the bolete family that has reduced its tube layer to a set of thick radial plates, and traces of its ancestry keep showing through: cross-veins between the gills, occasional pored patches near the stipe apex, bolete-shaped spores and a bolete-coloured spore deposit.

Reading the Cap

The cap measures roughly 3-8 cm across, convex at first, then flattening and often becoming shallowly depressed at the centre in age, with a margin that starts inrolled and gradually straightens. The surface is dry throughout - never greasy, never viscid - and finely tomentose or suede-like when fresh, a texture best judged by drawing a fingertip across it rather than by eye.

Colour ranges through reddish-brown, cinnamon, tawny, olive-brown and dull chestnut, usually darker at the centre and fading toward the margin in older or sun-bleached specimens. With age or in dry weather the cap surface commonly cracks into small tiles, and pale yellow flesh shows in the fissures - a helpful supporting character, since the yellow undercolour is much stronger here than in most similarly sized brown-capped gilled mushrooms.

The Spore-Bearing Surface

This is where you spend most of your time. The gills are true blade-like plates, not blunt ridges, and their qualities are distinctive:

• Colour: deep chrome to golden yellow while fresh, sometimes with an olive cast in age, occasionally developing dull greenish-blue stains where bruised. That bruising reaction is variable - present and obvious in some collections, absent in others - so treat it as confirmatory rather than required.
• Spacing: distinctly distant, so you can count individual gills easily; nothing like the crowded packing of a Hygrophoropsis or a Paxillus.
• Thickness: thick and slightly waxy in appearance, breaking rather than folding when you push a fingernail sideways across them.
• Attachment: strongly decurrent, running well down onto the stipe.
• Veining: the space between adjacent gills is crossed by low connecting veins, and near the stipe apex the veining sometimes closes into shallow pits or short tubes. Finding even a small poroid patch there is close to a confirmation of the genus.

Stipe and Base

The stipe is 3-8 cm long and 0.5-1.5 cm thick, usually tapering downward, solid, dry and without a ring or a net. Its upper part is yellow, often finely granular-punctate under a lens, while the lower part is flushed reddish-brown, ochre or rusty, the same family of colours as the cap.

Dig rather than pluck. In Phylloporus rhodoxanthus the base carries bright yellow mycelium and yellow mycelial strands that bind soil, moss and litter into a small ball. Basal mycelium colour is one of the practical separators within the genus, and you only get it if you lift the whole fruit body out of the ground with a knife or your fingers.

Flesh and Colour Change

Split a fruit body lengthwise. The cap flesh is whitish to pale yellow, and the stipe flesh is yellow, often intensely chrome yellow in the lower half. In some collections the cut surface goes faintly and slowly blue in the cap, but the reaction is weak and inconsistent; a total absence of blueing does not argue against the identification. Odour is mild and unremarkable, and the flesh is soft rather than fibrous.

Taking and Reading a Spore Print

The spore print is the decisive test, because it puts this mushroom firmly on the bolete side of a group of yellow-gilled imitators that all have pale prints. Cut the cap free, lay it gills-down on white card, cover it with a cup to keep humidity in, and leave it two to four hours or overnight. The deposit is olive-brown to yellowish-brown - never white, never salmon, never smoky grey.

Under a microscope the spores are smooth, subfusiform and roughly 9-14 by 3.5-5 micrometres, exactly the elongate shape you expect from a bolete rather than the small ellipsoids of a typical gilled mushroom.

Substrate, Season and Ecology

Phylloporus rhodoxanthus is ectomycorrhizal, forming root partnerships with trees rather than rotting wood, and it is most consistently associated with oaks, with records under other broadleaves and under conifers such as pine and hemlock. Look on bare or mossy soil along trail cuts, on shaded banks, in leaf litter over poor acidic ground - never fruiting from wood, never in dense clusters from a single base. Fruiting runs from midsummer into early autumn, peaking during humid spells, and specimens are usually solitary or in loose groups of two or three.

Separating the Look-alikes on Morphology Alone

• Hygrophoropsis aurantiaca. Similar orange-yellow decurrent gills, but they are thin, crowded and repeatedly forked, the cap is downy orange rather than velvety reddish-brown, the flesh is thin and pliant, and the spore print is white. It grows on conifer litter, wood chips and rotting wood.
• Chroogomphus. Thick, distant, decurrent gills again, but they are grey to smoky and eventually near black, the flesh is salmon-orange, there is a fibrillose veil zone on the stipe, and the spore print is smoky grey-black.
• Paxillus involutus. The margin is strongly and persistently inrolled and felted, the gills are crowded, olive-brown, easily peeled away from the cap flesh as a sheet, and they stain rust-brown to blackish where pressed; the print is yellow-brown.
• Cantharellus. The underside carries blunt, rounded, forking ridges rather than blade-like gills, the flesh tears into fibrous strings, and the whole fruit body is one continuous piece of tissue.
• Pore-bearing relatives. Xerocomellus and Aureoboletus species share the dry cracking cap but retain an ordinary tube layer.
• Other Phylloporus. Phylloporus leucomycelinus is a close match above ground but has white basal mycelium, which is why lifting the base matters.