Minnesota Seasons - Hammered Shield Lichen


Conservation Status	IUCN Red List	not listed

	NatureServe	NNR - Unranked

	Minnesota	not listed

Occurrence	Widespread and abundant
Habitat/Hosts	Open habitats, disturbed sites, and agricultural lands. Trees and mossy rock.

				Photo by Luciearl

Identification	Hammered Shield Lichen is a widespread, abundant, weedy lichen. It occurs across the northern hemisphere, in southern Africa, and in Australia. It is very common in Minnesota. It grows on the bark of deciduous and coniferous trees in relatively open habitats, disturbed sites, and agricultural lands. It also grows on mossy rock, but only rarely grows on soil. The vegetative body (thallus) is leaf-like (foliose), greenish-gray to whitish-gray, more or less circular in outline, and divided into branches (lobes). The lobes are flat, 1 ⁄16″ to 3 ⁄16″ (2 to 5 mm) wide, widely spreading, overlapping, and touching but separate, not fused together. The tips are abruptly squared, as if cut off (truncate). The upper surface is shiny but sometimes has a white, flour-like or frost-like covering (pruinose). It has abundant powdery granules (soredia). It does not have shiny granules (isidia). It may be smooth but usually has a network of sharp ridges and depressions giving it a “hammered” appearance. It has minute, elongated, rounded openings (pseudocyphellae), and sometimes develops cracks along prominent pseudocyphellae. The lower thallus surface is black and is moderately to densely covered with black, unbranched root-like structures (rhizines). When wet, the thallus can usually be removed intact with a knife. Hammered Shield Lichen rarely produces disk-like spore producing structures (apothecia). When present, they are 1 ⁄16″ to 5 ⁄16″ (2 to 8 mm) wide and have a dark brown disc.

Similar Species

Distribution			Sources: 4, 24, 26, 29 , 30, 77, 81.

Comments	What’s in a Name? The “Hammered” in one common name refers to the network of sharp ridges and depressions that give the lichen a “hammered” appearance. Crottles are various lichens that were used to make dyes. Parmelia sulcata, sometimes called “Powdered Crottle”, was used as the source for a reddish-brown dye.

Taxonomy	Division:	Ascomycota (sac fungi)
	No Rank:	saccharomyceta
	Subdivision:	Pezizomycotina
	No Rank:	leotiomyceta
	Class:	Lecanoromycetes
	Subclass:	Lecanoromycetidae
	Order:	Lecanorales
	Suborder:	Lecanorineae
	Family:	Parmeliaceae (shield lichens and allies)
	Mycobiont:	Parmelia sulcata
	Photobiont:

Synonyms	Parmotrema sulcata Parmotrema sulcatum

Common Names	Cracked-shield Lichen Furrowed Shield Lichen Hammered Shield Lichen Powdered Crottle Powdered Shield Waxpaper 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

The 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: isidia.

Rhizine

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

Soredium

The reproductive structure of a lichen consisting of a cluster of algal cells (the photobiont) wrapped in fungal filaments (the mycobiont). Plural: soredia.

Thallus

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


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Luciearl



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Luciearl 11/4/2019	Location: Superior Hiking Trail, Cook County




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Hammered Shield Lichen

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