Minnesota Seasons - Smooth Axil-bristle Lichen

Conservation • Description • Ecology • Distribution • Taxonomy


Conservation Status
IUCN Red List	not listed
NatureServe	NNR - Unranked
Minnesota	not listed

Description

Smooth Axil-bristle Lichen is a small to medium-sized lichen that grows on the bark of deciduous trees, rarely on rock.

The vegetative body (thallus) is leaf-like (foliose) and divided into lobes. It is attached to the substrate (bark) by abundant, uniformly distributed, black, usually unbranched, anchoring structures (rhizines). The lobes are 1 ⁄32″ to 1 ⁄16″ (0.8 to 2 mm) in diameter, flat, and closely appressed to the substrate. The upperside is pale gray to bluish-gray and wrinkled or corrugated in the center. The surface has neither powdery dull granules (soredia) nor shiny granules (isidia). The underside is black. There are short, black, hair-like appendages in the axils of the lobes and sometimes also on the margins. These may not be visible without a hand lens. The interior of the thallus is divided into two layers. The lower layer (medulla) is yellowish, though this may be difficult to see except under the apothecia.

Disk-like, spore-producing structures (apothecia) are usually abundant. The disks are 1 ⁄16″to 3 ⁄16″ in diameter, reddish-brown, and shaped like a plate. Each disk has a ring of tissue around it that resembles the tissue of the vegetative (non-fruiting) part of the lichen.

Similar Species

Powdery Axil-bristle Lichen (Myelochroa aurulenta) has dull, powdery granules (soredia) on the surface that can be easily brushed off.

Rock Axil-bristle Lichen (Myelochroa obsessa) grows only on rocks. The surface is somewhat shiny and is covered with shiny granules (isidia).

Ecology

Substrate

Trees

Growth Form

Foliose

Habitat

Open woods, roadsides.

Hosts

Hardwood trees.


Distribution
		Sources 4, 7, 24, 26, 29, 30, 77, 81.
3/11/2025

Occurrence
Common in eastern United States and in northern Minnesota


Taxonomy
Kingdom	Fungi (fungi)
Subkingdom	Dikarya
Phylum	Ascomycota (sac fungi)
Subphylum	Pezizomycotina
Class	Lecanoromycetes (common lichens)
Subclass	Lecanoromycetidae (shield lichens, sunburst lichens, rosette lichens, and allies)
Order	Lecanorales (shield lichens, rim lichens, and allies)
Suborder	Lecanorineae
Family	Parmeliaceae (shield lichens and allies)
Subfamily	Parmelioideae (typical shield lichens)
Genus	Myelochroa
Mycobiont	Myelochroa galbina
Photobiont

Subordinate Taxa


Synonyms
Parmelina galbina Parmelina subquercifolia Parmelina galbina

Common Names
Smooth Axil-bristle Lichen

Glossary

Apothecium

An open, disk-shaped or cup-shaped, reproductive structure, with spore sacs on the upper surface, that produces spores for the fungal partner of a lichen. Plural: apothecia.

Foliose

Adjective: Leaf-like growth form; referring to lichens with leaf-like growths divided into lobes.
Noun: The leaf-like, vegetative body of a lichen (thallus) that has thin, flat lobes which are free from the substrate.

Isidium

An asexual reproductive structure of a lichen consisting of a cluster of algal cells (the photobiont) wrapped in fungal filaments (the mycobiont) and enclosed within a layer of protective tissue (cortex). Plural: insidia.

Rhizine

A root-like structure of a lichen that attaches the lower layer to the substrate.

Soredium

An asexual reproductive structure of a lichen in the form of a tiny dull granule on the thallus surface that can be easily brushed off. It consists of a cluster of algal cells (the photobiont) wrapped in fungal filaments (the mycobiont), but without an outer layer of protective tissue (cortex). Plural: soredia.

Thallus

The vegetative body of a lichen composed of both the alga and the fungus.


Visitor Photos

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Dan W. Andree

Lichens on Aspen tree trunk...

I came across this one on a fairly mature aspen trunk in that aspen/bur oak mix grove near the east end at the Frenchman’s Bluff SNA. I am sure when all leafed out it would be very slow walking in there. Noticed mainly bur oak and aspen as main trees, but a variety of smaller plants some with pokers or a lot of spikes on them. Anyway interesting just to see what was in there...3-8-25 The larger or main one may be foliose lichen but I’m not sure.

Alfredo Colon


Honey Fae (Farah)


Luciearl


MinnesotaSeasons.com Photos



		Thallus


Lichen


Apothecia		Apothecia

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Visitor Sightings

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Dan W. Andree
3/8/2025

Location: Frenchman’s Bluff SNA

I came across this one on a fairly mature aspen trunk in that aspen/bur oak mix grove near the east end at the Frenchman’s Bluff SNA. I am sure when all leafed out it would be very slow walking in there. Noticed mainly bur oak and aspen as main trees, but a variety of smaller plants some with pokers or a lot of spikes on them. Anyway interesting just to see what was in there...3-8-25 The larger or main one may be foliose lichen but I’m not sure.