Appalachian Field Note / AIG-000012

Black Tooth

cf. Phellodon niger

I thought somebody had pressed a burnt log into the wet leaves. Then I got down on the litter, tipped a rim, and there it was: a whole ceiling of pale teeth, packed like a comb, hanging in the dark.

July 25, 2026
Exercise Trail #344
Pisgah National Forest
Natural notes and photographs by Will Thomas

Natural note

The forest floor had grown a set of teeth

Here is the trick, and it is a good one. From above, this fungus is all smoke and frost: black basins, grey zones, and thick white rims shoving through the litter like ice on a pond. The real machinery hangs underneath. Thousands of pale spines, each one lined with the microscopic cells that fire spores into moving air.

The group is consistent with Black Tooth, Phellodon niger (Fr.) P. Karst., type species of its genus and a stipitate hydnoid in the family Bankeraceae, order Thelephorales. I want to be precise about that name. Modern DNA work has shown that several dark Phellodon lineages can wear variations of this same charcoal costume. North American populations may even be a cryptic species; ITS sequences from the southern United States sit only 92 to 93 percent similar to United Kingdom material. What I photographed looks strikingly typical. I did not section a stalk, run KOH, measure a spore, sample a root tip, or send a barcode. This is a strong field comparison, not a laboratory conclusion.

Turn the mushroom over

A tooth is a gill turned into a stalactite

Gills, pores, and teeth solve the same engineering problem: fit a huge fertile surface under a relatively small cap. Phellodon chooses the tooth plan, and once you see it you cannot unsee it.

More surface, more basidiaEach spine carries a hymenium, the spore-producing tissue. Packing many spines under the cap multiplies the available reproductive surface without building a bigger umbrella.
Gravity gets a clean runwayMature basidiospores are discharged from the sides of the teeth into the open spaces between them, then fall clear of the cap. Literature sizes for P. niger are tiny: roughly 3.5 to 5 by 3 to 4 micrometers, hyaline, ellipsoid, and ornamented. I did not measure these.
The teeth follow the stalkIn these photographs, the spines continue down toward dark central tissue. Mycologists call that arrangement decurrent. The teeth start pale blue-grey and age toward mid-grey.

Low macro view beneath probable Black Tooth caps showing dense pale grey spines descending toward dark partly buried stalk tissue — The fertile surface is not black. The cap is charcoal above, while its pale grey teeth hang underneath.

Why the comparison fits

Six clues in a two-minute encounter

Black centers

Older cap tissue is deep charcoal to black, not merely brown. The center darkens while the outer growth remains pale. That darkening is the field mark that gave Fries the epithet nigrum in 1815.

White active rims

Broad, lobed, white to grey margins ring the darker centers. In wet weather the growing edge can even bead black liquid. The contrast is one of the strongest marks in the sequence.

Fused architecture

Several fruiting bodies have collided and grown together, building compound rosettes rather than neat separate umbrellas. Neighboring caps of Phellodon do this as a matter of habit.

Rough zoned caps

The upper surface is matted, pitted, lumpy, and concentrically graded from pale margin to darker center. Needles and leaf bits get trapped as the rim expands. They are obstacles, not food.

Pale teeth

The underside carries tightly packed grey-white spines. There are no gills and no sponge-like pore surface. If you only remember one flip-the-cap lesson from this trail, make it this one.

Dark buried base

Nearly black central tissue disappears into decomposed wood, humus, and leaf litter. The stipe often wears a spongy mycelial coat that soaks water like felt. A cut section was not made.

The missing character is inside the stalk. A classic technical distinction is the duplex context: a darker, firmer core wrapped in a softer tomentose outer layer. The camera shows dark basal tissue but not a clean section. Phellodon confluens, P. melaleucus, and other members of the modern P. niger complex remain part of the differential.

The real animal is underground

This mushroom is the flag above a buried economy

The cap is temporary. The enduring organism is a web of hyphae in soil and on living root tips. That network trades with a tree, and it may also nibble carbon that did not come straight from a leaf.

01 / Sunlight

The tree fixes carbon

Leaves use light to build sugars. Some of that photosynthetic carbon moves below ground through the roots and becomes fungal currency.

02 / Contact

Fungus wraps the root

Ectomycorrhizal hyphae form an external mantle and grow between root cells rather than simply digesting dead wood. On Norway spruce, P. niger even makes distinctive chlamydospores.

03 / Exploration

Hyphae enter tiny soil spaces

Threads far narrower than roots explore mineral surfaces and water films, extending the effective reach of the root system into places a tree cannot go alone.

04 / Fruiting

The black rosette appears

When moisture, temperature, resources, and development align, the hidden organism invests in a spore-producing structure. Then, if you are lucky, you trip over it.

That is why a rotten-looking chunk of wood beneath the caps can be misleading. The fruiting body may push through decomposed material, but the ecological partnership extends into living roots nearby. Stable-isotope work on ¹³C puts P. niger closer to saprotrophic fungi than to many strict ectomycorrhizal species, which hints that it can acquire some carbon from sources other than a living host. The host tree in this encounter was not identified.

Secondary metabolism

This charcoal stub is running a diterpenoid factory

This is the part that makes me want to grab you by the sleeve. That corky black rosette is packed with molecules from the same structural family that cell biologists use when they ask cultured glia to release nerve growth factor. The isolation papers on P. niger solved structures. They did not turn this fungus into a medicine.

Fang, Zhang, Li, Li, and Liu, working with fruitbodies collected in Yunnan, isolated nigernins A and B plus the nitrogenous terphenyl phellodonin in 2010. In 2011 the same group added nigernins C through F. Nigernin F is the show-stopper of the set: a 3,4-seco cyathane, meaning the bond between carbons 3 and 4 of the five-membered ring has been oxidatively cleaved. That ring-opened framework had not been found in nature before.

Cyathane diterpenoids are built on a 5/6/7 fused-ring system: a five-membered ring fused to a six-membered ring that is itself fused to a seven-membered ring. Nigernin A is cyatha-3,12-diene-15-oic acid, formula C₂₀H₃₀O₂. Nigernin B is the isomeric (3S*,4R*)-cyatha-12,18-diene-15-oic acid. Both carry a carboxylic acid at C-15 rather than the methyl group seen in the biosynthetic intermediate cyatha-3,12-diene. Nigernin F is a 3,4-seco cyathane whose opened C-3/C-4 edge carries two keto carbonyls, among other oxygenation that the isolation paper maps in full. Phellodonin is a heavily substituted nitrogenous p-terphenyl (C₃₉H₄₂N₂O₁₅) with an N,N-dioxide benzodioxazine core. The primary papers report the real structures: Fang et al. 2010 for nigernins A and B plus phellodonin, Fang et al. 2011 for nigernins C through F, and Usui, Lin, Masuda, and Baran 2013 for the synthetic confirmation of phellodonin.

The three images below are not photographs and not molecular diagrams. They are generated editorial illustrations. Rings and cells are conceptual. For the actual bond-and-atom structures, use the isolation and synthesis papers linked in the sources.

Generated editorial illustration of a conceptual cyathane ring framework associated with nigernins from Black Tooth. Not a photograph and not a molecular diagram.

Generated editorial illustration of cultured cells with branching neurites, used to represent NGF-associated outgrowth reported for some cyathane diterpenoids from other fungi. Not a photograph of Phellodon niger chemistry.

Generated editorial illustration of laboratory microglia-like cells, used to represent anti-inflammatory findings reported for selected cyathanes in microglial models. Not a photograph and not a structure of phellodonin.

I want this said plainly, because the chemistry is exciting enough without embroidery. Fang's 2010 and 2011 papers are structure papers. They did not run the full NGF, PC-12, or microglial assay panel on nigernins A through F. The medical interest is real and specific: these compounds occupy the same structural continuum as documented neurotrophic and neuroprotective cyathanes. That is a hypothesis generator, not a prescription. This fruiting body is fibrous, durable, and treated as inedible. Nobody should eat Black Tooth to "regrow nerves."

The same 2010 extract also gave phellodonin and three known companions: 2',3'-diacetoxy-3,4,5',6',4''-pentahydroxy-p-terphenyl, grifolin, and 4-O-methylgrifolic acid. Grifolin-type prenylated phenolics are widely reported as antioxidant, cytotoxic, and antimicrobial. Thelephoric acid is the house pigment of the Thelephorales and a large part of why these fungi look scorched. It arises on the shikimate / p-terphenyl pathway, but it is not a simple 2,5-diphenyl-1,4-benzoquinone. The established structure is a fused, oxygen-bridged benzobisbenzofuran quinone: 2,3,8,9-tetrahydroxybenzo[1,2-b:4,5-b']bisbenzofuran-6,12-dione, solved and synthesized by Gripenberg. Together those quinones and phenolics are the chemical defense kit, the dye kit, and the reason a dried specimen can smell like fenugreek.

How you would know a nigernin

In ¹³C NMR, look for the cyathane skeleton: angular methyls, olefinic carbons of the diene, and the C-15 carboxyl near 170 to 173 ppm. HR-MS returns a C₂₀ formula. ROESY (for example H-5 against specific methyls) sets relative configuration. The seco series loses the C-3 to C-4 connection and gains new carbonyl features from cleavage.

How you would know phellodonin

Aromatic p-terphenyl signals, multiple acetoxy methyls near 2.0 ppm and 168 to 170 ppm, an N-methoxy, exchangeable phenolic protons, and the low-field carbons of the N,N-dioxide benzodioxazine. HR-ESI-MS of the sodium adduct, plus comparison with sarcodonin data, is definitive. Synthesis closed the argument.

How they pull it out of a cap

Typical workflow: chloroform/methanol extraction of dried fruitbodies, silica-gel chromatography with petroleum ether-acetone gradients, then Sephadex LH-20 or another silica column. I did none of that on the Davidson River collection. The chemistry here is literature chemistry, sitting next to photographs of an uncollected organism and three generated illustrations that are not molecular diagrams.

This is not a medicinal guide. Related cyathanes have published neurotrophic and anti-neuroinflammatory activity in cell systems. Nigernins have published structures. Between those two sentences sits a lot of work that has not been done on this species, and none of it was done on this patch of Pisgah litter.

Photography sequence

Charcoal, frost, and a hidden comb

Several probable Black Tooth fruiting bodies fused over decomposed wood, with white margins, black centers, buried dark stalks, and a small exposed patch of teeth — 01Separate caps collide, fuse, and turn a patch of forest floor into one compound fruiting structure.

Close overhead view of fused probable Black Tooth caps with white margins, grey zones, black centers, water beads, and embedded leaf litter — 02Water beads on the pale margin. Charcoal tissue occupies the older center.

Oblique macro view of a black pitted tooth-fungus cap center ringed by a pale margin among wet hardwood leaves — 03The cap is not smooth. Its center is matted, pitted, and interrupted by smaller lobes.

Tight macro view of charcoal cap texture, grey zones, pale lobed margins, and leaf fragments held by a probable Black Tooth cluster — 04Leaves caught between the lobes record growth through litter. They are obstacles, not prey.

A field identification under cross-examination

What would move this from probable to documented?

A photograph can settle the broad architecture. It cannot show every character that modern Phellodon taxonomy asks us to inspect. I love that tension. It keeps the science honest.

Recent sequencing work expanded the known European genus from seven species to thirteen and split new species from the old P. niger species complex. One practical consequence is refreshingly direct: when a collection is not textbook-perfect, a confident species name may require DNA.

Characters photographed or left untested in observation AIG-000012
Compound dark caps	Photographed	Strong support for dark Phellodon.
Pale decurrent teeth	Photographed	Confirms a hydnoid fertile surface.
Duplex stalk context	Not checked	Requires a clean longitudinal section.
KOH reaction	Not checked	A bluish-green response can support the complex.
Drying odor	Not recorded	Fenugreek, curry, or lovage-like notes appear in some treatments.
Spores	Not collected	Print color, size, shape, and ornamentation remain unknown here.
ITS barcode	Not sequenced	Needed to place an ambiguous collection among cryptic lineages.
Root partner	Not sampled	Nearby tree presence is not proof of a specific host connection.

One weird thing

The mushroom can disappear while the organism stays put

Imagine surveying this patch next year. No black caps. No white rims. No teeth. It would be easy to record an absence, yet fungal DNA and living mycorrhizal root tips may still occupy the soil.

That mismatch has real consequences for fungal monitoring. A cap is an event, not the whole individual. Researchers working with stipitate hydnoid fungi have used species-specific molecular markers to detect below-ground material in years without fruiting, sometimes four years after the last visible rosette. The forest can therefore retain a fungal resident whose reproductive architecture is temporarily invisible. In Britain the species is treated as rare; in Switzerland it is listed as vulnerable. Conservation surveys that only count caps will undercount the organism.

The encounter lasted less than two minutes. The organism that produced it may have been negotiating with roots beneath those leaves for years.

The special frame

White Carnival Candy Slime Mold built a city on a log

Now shrink yourself to the scale of a pinhead. The smooth forest log becomes a ridge system, and hundreds of pale towers rise from it. This is consistent with White Carnival Candy Slime Mold, cf. Arcyria cinerea.

The phrase slime mold sounds like a fungus with unfortunate branding. Biologically, this organism is an amoebozoan. During its feeding phase it is mobile, lacks a fixed fruiting shape, and engulfs microscopic food. The structures in the photograph are its reproductive architecture, not tiny mushrooms. I still stop for them every time. They are a whole kingdom of life doing city-planning on rotten wood.

Focus-stacked macro landscape of hundreds of minute white to ash-grey Arcyria-like sporocarps, compared with Arcyria cinerea, rising from decaying wood — Hundreds of pale sporocarps rise from decaying wood. The image strongly supports *Arcyria*; species-level separation requires characters far smaller than the frame can resolve.

Spore

A microscopic spore germinates into an amoeboid cell or, in wet conditions, a flagellated swarm cell.

Mobile feeder

Compatible cells ultimately form a multinucleate plasmodium that moves through the substrate and engulfs bacteria and other microscopic food.

Architecture switch

The roaming mass reorganizes. Mobile feeding tissue becomes a crowded field of upright reproductive towers.

Timed release

A net of elastic capillitium threads holds and gradually exposes spores for dispersal after most of the outer wall disappears.

Why the name remains qualified. A traditional description of A. cinerea includes pale ovate to cylindrical sporocarps about 0.3 to 4 mm tall, a small persistent basal cup called a calyculus, a capillitium firmly attached to that cup, threads ornamented with tiny spines or warts, and spores around 6 to 7 micrometers across. The photograph records the colony brilliantly, but not those microscopic characters. A 2025 phylogenetic analysis also found specimens called A. cinerea scattered across twenty branches, evidence that the familiar morphospecies contains unresolved genetic diversity.

Names that describe the machinery

Cork tooth, black tooth, ash-grey tower

Phellodon

Cork plus tooth

The genus name combines roots for cork and tooth. It captures both the tough texture reported for the fruiting body and the hydnoid surface underneath. Karsten built the genus in 1881 around this species.

niger

The black one

The Latin epithet points directly to the blackening cap. Fries first described it as Hydnum nigrum in 1815; Karsten moved it to Phellodon in 1881. English names include Black Tooth and black scented spine fungus.

cinerea

Ash-grey

The slime mold's epithet describes its pale grey mature fruiting structures. The common name turns the same crowded colony into carnival candy.

Colors sampled from the photographs

Active margin, charcoal basin, carnival ash

Active Marginpale growing edge#E8E4D8

Blue-Grey Teethfertile spines#9A978C

Charcoal Basinolder cap center#24211D

Rain-Soaked Oakwet leaf litter#6B3F25

Carnival AshArcyria sporocarps#D8D2CF

These values are editorial samples from the photographs, not calibrated measurements of either organism. Lighting, processing, water, and surrounding leaves influence every pixel.

Those same terphenylquinones and phenolics are why dyers hunt this fungus. Fruitbodies yield gray-blue to green on wool and silk, shifting toward teal, slate, and olive depending on mordant and pH.

Protein fibers

Wool and silk take the cool tones most cleanly. Iron, alum, tin, and copper each shove the hue. The Mushroom Color Atlas records separate baths on wool, silk, and linen.

Keep it alkaline

Baths around pH 9, often held with soda ash, are preferred. Cellulose fibers like that alkaline environment. A brown tinge in the pot is normal for tooth fungi and usually washes out.

What the metals are doing

Thelephoric acid and related phenolics complex with metal ions. That is how you get fastness and the muted cool tones that are hard to steal from plants alone.

I looked for a specific Nahuatl cosmogonic pairing of this species with edible trumpet mushrooms. Ethnomycological literature records Phellodon in Mexico, and black trumpets (Craterellus) are well-known edibles in many traditions. A named cosmogonic counterpart relationship for P. niger itself is not sitting in the accessible scientific or ethnohistorical sources the way teonanácatl is. The dye use, by contrast, is firmly documented in modern fiber practice and matches a longer exploitation of pigmented Thelephorales.

Keep walking the same trail

Other Davidson River field notes

Fungus on fungusWitches' ButterA yellow jelly parasite on wet wood from the same trail and afternoon. Root partnershipShaggy-stalked boleteAnother ectomycorrhizal fruiting body pushing through saturated forest litter. Wood decayChicken of the WoodsA true wood-decay fungus, useful for contrasting trophic strategies. ParasitismBolete moldA fungus using another mushroom as both address and food source. Same forestCarmine-pored boleteA red-pored photographic comparison from the Davidson River woods. Same forestOrnate-stalked boleteA reticulate bolete with its own suite of field characters and uncertainties.

Field record

Davidson River, after rain

Observation: AIG-000012
Date: July 25, 2026
Time: 2:41 p.m. to 2:43 p.m.
Location: Exercise Trail #344 near Davidson River Campground, Pisgah National Forest
Coordinates: 35.28275, −82.7242667
Elevation: 663.4 m
Author: Will Thomas, Wikimedia Commons
Disposition: Photographed in place and left undisturbed

References