Lichen Flora of Eastern North America:
The Genus Parmelia Sensu Stricto
James W. Hinds

Department of Biological Sciences
University of Maine, 5722 Deering Hall, Orono, ME 04469-5722

ABSTRACT: Descriptions, keys, distribution maps, and illustrations are provided for the 7 species of Parmelia sensu stricto found in eastern North America (eNA): fertilis, fraudans, neodiscordans, omphalodes, saxatilis, squarrosa, and sulcata. The species with the most restricted ranges in eNA are P. fertilis, known only from southeastern Canada and Maine, and P. neodiscordans, restricted to the Appalachians from North Carolina to Maine.  P. fraudans has the most northerly range, extending into the U.S. only in Minnesota and Michigan.  P. omphalodes and P. saxatilis have very similar, boreal ranges, but P. saxatilis extends  farther south into southern Ontario and along the Atlantic coast to Long Island, NY.  The range of P. squarrosa is the most southerly, ranging south to Arkansas, Alabama, and South Carolina; in eNA it is found as far north as the fiftieth latitude, with a distribution overlapping broadly with that of P. saxatilis from the Great Lakes area through New York and New England to Quebec and Newfoundland.  P. sulcata is the only Parmelia species commonly found in agricultural regions of the northern Midwest region of the U.S. and southern Ontario.

This review of the lichen genus Parmelia in eastern North America (eNA) is the first of a series of generic reviews by various authors that will, it is hoped, eventually cover all of the lichens of eNA, a region defined as extending from the arctic/boreal boundary at about 54° N., south to Florida and west to the midgrass/tallgrass boundary at about 97° W. It is planned that each generic treatment will include descriptions, keys, detailed distribution maps, and illustrations.

In the present study, distribution maps are based on specimens examined by the author and others (see Acknowledgments) as well as literature reports considered by the author to be reliable. The only distributional references cited, however, are those that include records not found in the specimens examined. A detailed list of every accepted specimen and literature report may be obtained from the author upon request. Herbaria have been abbreviated following Holmgren et al. (1990), except for the following private herbaria: CLAYDEN, DIRIG, HINDS, LADD, LAY, and SCHMITT. Distribution maps have been generated using decimal latitudes and longitudes and MapInfo Desktop software. References singled out as "Key References" below are not usually specifically cited in the text, even though they were relied upon in many instances, for example for chemistry and for spore, conidial, and anatomical measurements.

PARMELIA Ach., Meth. Lich.: 153 (1803). Shield Lichens. Etymology (Feige 1996): Greek parme, a fruit bowl + -eileo, enclosed, alluding probably to the lecanorine apothecia.

TYPE SPECIES: Parmelia saxatilis (L.) Ach.

KEY REFERENCES: Hale 1971, 1987; Skult 1987.

SELECTED PREVIOUS ILLUSTRATIONS: Color photos: McCune & Geiser 1997 (saxatilis, sulcata), Wirth 1995 (omphalodes, saxatilis, sulcata); B & W photos: Hale 1987 (all species in eNA), Hyvönen 1985 (squarrosa); Drawings: Brodo 1988 (sulcata), McCune & Geiser 1997 (squarrosa, sulcata), Thomson 1984 (fraudans, omphalodes, saxatilis).

HISTORY OF GENUS: Parmelia has had a remarkable contraction of concept, from Acharius' broad concept in 1803 of almost all crustose, foliose, and fruticose species with lecanorine apothecia to Hale's (1987) narrow concept of an adnate, eciliate, pseudocyphellate foliose species with black lower surface, rhizines, cylindrical microconidia < 8 m m long, simple spores 8 per ascus, and atranorin, not usnic acid, in the cortex. By the end of the 19th century Parmelia was generally held to include only foliose species with rhizines (excluding, e.g., Hypogymnia, Lobaria, and Pannaria), laminal apothecia (excluding, e.g., Cetraria), and simple spores (excluding, e.g., Physcia and Xanthoria). Starting in the mid-19th century with Massalongo's separation of Menegazzia, there were attempts to circumscribe the vast assemblage of species contained in Parmelia, with varying degrees of acceptance. Many of the proposed segregates are based largely on thalline characters, rather than purely fungal characters, and this has slowed their acceptance (e.g., Purvis et al. 1992)

VEGETATIVE STRUCTURES: Thallus foliose, 4-60 cm broad (in eNA, 5-30 cm), greenish to whitish mineral gray, or in some species turning brown or black in exposed habitats, with sublinear lobes divaricate, contiguous, or imbricate and 0.5-10 mm wide (in eNA 0.5-5 mm). Upper surface plane to foveolate, becoming cracked with age, and isidiate, sorediate, or lacking soredia and isidia, sometimes with a white pruina of oxalates, and always with pseudocyphellae appearing as irregular laminal or marginal white markings, often fusing into a loose reticulate network. Lower surface black with simple, furcate, or squarrosely branched rhizines, 0.5-2 mm long. Upper cortex paraplectenchymous and 4-6 cells thick (20-30 mm), algal layer and medulla 100-200 mm thick, and lower cortex less than 20 mm thick. Pseudocyphellae consisting of areas where the cortex has disintegrated and become filled with medullary hyphae, covered often by a thin, densely pored, polysaccharide layer.

REPRODUCTIVE STRUCTURES: Apothecia adnate to substipitate, 1-20 mm in diameter (in eNA, 1-12 mm), and disk brown or reddish brown with the rim usually pseudocyphellate and rugose; spores 8 per ascus and in eNA 10-18 x 5-11 mm. Pycnidia immersed and laminal with conidia usually cylindrical, 5.5-8 mm long.

CHEMISTRY: All species have atranorin and chloroatranorin in the cortex. Six of the seven species in eNA have salazinic acid in the medulla; one species, P. neodiscordans, has fumarprotocetraric acid in the medulla.

DISTRIBUTION AND SUBSTRATES: The center of evolution for Parmelia appears to be in eastern Asia and in Australia and New Zealand, with 12 and 14 species, respectively. Seven species occur on trees and rock in eNA, most commonly in northern regions but with one or more species found at least occasionally in most of the region, exclusive of the southeastern coastal plain.


1. Sorediate 2
1. Not sorediate 3
2. Soredia laminal and marginal, white, granular; rhizines simple to squarrosely branched; pseudocyphellae laminal and marginal; on trees and rock
P. sulcata
2. Soredia coarsely isidioid when mature, mostly marginal, yellowish (usnic acid); rhizines simple to furcate; pseudo-cyphellae mostly marginal; usually on rock
P. fraudans
3. Isidiate 4
3. Not isidiate (but can have secondary lobules) 6
4. Isidia coarsely granular (actually soredia), mostly marginal
P. fraudans
4. Isidia fine and cylindrical; laminal and marginal
5. Rhizines squarrosely branched (simple at lobe margins) [if necessary, use knife to scrape rhizines onto white paper to visualize]; most common on trees P. squarrosa
5. Rhizines simple or furcate, rarely subsquarrosely branched; most common on rocks P. saxatilis
6. Medulla K- (or K+ yellowish turning dingy brown), P+ red [fumarprotocetraric acid]; lobes small, 0.5-2 mm wide with pseudocyphellae usually restricted to margins and forming a white line there
P. neodiscordans
6. Medulla K+ yellow turning red, P+ orange [salazinic acid]; lobes generally larger (1-4 mm wide) with pseudocyphellae usually common laminally as well as marginally
7. Rhizines simple to squarrosely branched; on trees; apothecia common; rare, in southeastern Canada and Maine P. fertilis
7. Rhizines simple to furcate; on rocks; apothecia uncommon; widespread boreal species P. omphalodes

Parmelia fertilis Müll. Arg., Flora 70: 316 (1887). Type collection (Hale 1987): Siberia (G, lectotype); Syn: P. subdivaricata Asah.

Morphology: Thallus adnate on trees, greenish to whitish mineral gray, with divaricate, contiguous, or overlapping lobes 0.5-3 mm wide; upper surface plane to weakly foveolate with conspicuous marginal and laminal pseudocyphellae fusing with age into a reticulate network; rhizines simple to squarrosely branched. Pycnidia and apothecia common, the latter substipitate and 2-7 mm in diameter; spores rare, 12-14 x 6-8 mm.

Chemistry: Medulla contain-ing salazinic acid and con-salazinic acid (K+ yellow changing to red, P+ orange).

Distribution (map based on 15 sites: CANL, CLAYDEN, MAINE, NBM, US): P. fer-tilis is common in eastern Asia, but it has only recently been reported in eNA (Hale 1987, Gowan and Brodo 1988). All known sites in eNA are in southeastern Canada or Maine, including four from Fundy National Park in New Brunswick.

Remarks: Hale has suggested that P. fertilis is the parent morphotype to the isidiate P. squarrosa and the sorediate P. sulcata.

Parmelia fraudans (Nyl.) Nyl., Lich. Jap.: 28 (1890). Parmelia saxatilis (L.) Ach. * fraudans Nyl., Lich. Scand.: 100 (1861). Type collection (Hale 1987): Finland (H-NYL 34869, lectotype).

Morphology: Thallus adnate on rock (rarely on trees), greenish to yellowish to brownish mineral gray with contiguous to imbricate lobes 1-4 mm wide. Upper surface plane to rugose-foveolate with mostly marginal pseudo-cyphellae and coarsely granular, yellowish or grayish, densely clustered, mostly marginal, isidioid soredia; rhizines simple to furcate. Pycnidia and apothecia rare; spores 10-12 x 5-6 mm.

Chemistry: Medulla containing salazinic acid and protolichesterinic acid (K+ yellow changing to red, P+ orange); soralia with usnic acid.

Distribution (map based on 55 sites: CANL, CLAYDEN, MIN, NY, US, Ahti 1964, LeGallo 1952, Thomson 1984): P. fraudans is a boreal and arctic species that is rare in eNA except near Lake Superior. The report of Slack et al. (1993) of P. fraudans in Connecticut is probably erroneous (E. Lay, pers. comm.)

Remarks: P. fraudans is the only species in Parmelia s.s. to have usnic acid. Morpho-logically it closely resembles P. hygrophila Goward and Ahti of the Pacific Northwest (Goward et al. 1994), but differs from that species in its substrate (usually bark in P. hygrophila) and the position of its isidioid soredia (usually laminal in P. hygrophila).

Parmelia neodiscordans Hale, Smiths. Contr. Bot. 66: 1 (1987). Type collection (Hale 1987): USA, Maine, Acadia National Park (US, Hale 37496, holotype).

Morphology: Thallus adnate to loosely adnate on rocks, mineral gray to brownish, with imbricate lobes 0.5-2 mm wide, often with suberect lobules. Upper surface plane with pseudocyphellae forming a white marginal rim; rhizines simple. Pycnidia rare, apothecia not known.

Chemistry: Medulla containing fumarprotocetraric acid and accessory unidentified fatty acids (K-, P+ red).

Distribution (map based on 12 sites: CANL, DIRIG, DUKE, HINDS, MIN, NY): This species has only been recently described (Hale 1987) and in eNA is known only from the Appalachian Mountains from North Carolina to Maine.

Remarks: Morphologically P. neodiscordans resembles small- lobed, marginally pseudo-cyphellate morphotypes of P. omphalodes ("P. pinnatifida") as well as P. discordans Nyl. of Europe (although that species is generally darker) and P. skultii Hale of arctic regions (although that species generally has wider lobes and often has pruina). It differs from all these species, however, in having fumarprotocetraric acid as its principal medullary substance. Although Hale (1987) reported that the species was only found in the Appalachians, it appears that it also occurs rarely in western NA. Skult (1987) reported 3 forms with the same morphol-ogy and chemistry from western NA and in 1986 annotated two of these specimens (from the Yukon) at CANL as "P. neodiscordans Hale?".

Parmelia omphalodes (L.) Ach., Meth. Lich.: 204 (1803). Lichen omphalodes L., Spec. Plant.: 1143 (1753). Type collection (Hale 1987): specimens and Dillenius, 1742, pl. 24, fig. 80A (OXF, lectotype); Syn: P.omphalodes subsp. pinnatifida (Kurok.) Skult, P. pinnatifida Kurok.

Morphology: Thallus adnate to loosely adnate on rocks, often on talus slopes, and very rarely on base of tree growing out of cliff (HINDS), whitish mineral gray to brown to black, with imbricate lobes 1-4 mm wide, often with dense secondary lobes. Upper surface plane to weakly foveolate with pseudo-cyphellae marginal and laminal forming a distinct network to mostly marginal. Rhizines simple to furcate. Pycnidia common and apothecia uncommon; spores 10-15 x 7-9 m m.

Chemistry: Medulla containing salazinic acid with or without lobaric acid, consalazinic acid, and lichesterinic acid (K+ yellow changing to red, P+ orange). Also rarely with accessory galbinic acid, fumarprotocetraric acid, or protocetraric acid and several unidentified fatty acids.

Distribution: (map based on 124 sites: CUP, DUKE, HINDS, LADD, MAINE, MIN, NY, NYS, SCHMITT, US, Ahti 1964, Brodo 1984, Dey 1978, Gowan & Brodo 1988, Hale 1959, Lamb 1954, McQueen 1988, Skult 1987, Thomson 1984 [Canada only], 1993): Locally common on rocks in boreal and arctic Northern Hemisphere; in eNA found only in boreal habitats near Lake Superior and in the Appalachians northward. Skult (1987) reported a specimen from Cleveland, Ohio of W. Mudd (from "Aylon Moor"), but that specimen probably was from Cleveland, England.

Remarks: P. omphalodes is treated here as a morphologically variable species that includes small-lobed, marginally pseudocyphellate specimens that are found sparingly in eNA (known sites: alpine region of New Hampshire, Thunder Bay district of Ontario, and Labrador region of Newfoundland). This treatment follows Hale (1987) in not recognizing the small-lobed forms as subsp. pinnatifida (Kurok.) Skult. The presence of forms intermediate between broad-lobed and narrow-lobed forms as well as the lack of a consistent correlation between chemistry (the presence or absence of lobaric acid) and morphology (wide-lobed, laminally pseudocyphellate vs. narrow-lobed, marginally pseudocyphellate) [Skult 1987] makes it difficult to support a specific or subspecific status for the small-lobed morphotype.

Parmelia saxatilis (L.) Ach., Meth. Lich.: 204 (1803). Lichen saxatilis L., Spec. Plant.: 1142 (1753). Type collection (Hale 1987): Sweden (LINN, sheet 127361, lectotype). Syn: P. kerguelensis A. Wilson (Stenroos 1991).

Morphology: Thallus adnate to loosely adnate on rocks, less commonly on trees, rarely on soil and moss (US; Sirois et al. 1988), greenish mineral gray to brownish (especially at the lobe ends), with contiguous to crowded lobes, 1-4 mm wide. Upper surface reticulate-foveolate with laminal and marginal pseudocyphellae often forming a reticulate network; isidia cylindrical, simple to sparsely branched and up to 0.5 mm tall and becoming very dense in the older central part of the thallus. Rhizines simple to furcate, rarely subsquar-rosely branched. Pycnidia and apothecia uncommon; spores 16-18 x 9-11m m.

Chemistry: Medulla containing salazinic acid and accessory lobaric acid with or without protolichesterinic acid (K+ yellow changing to red, P+ orange). The percentage of specimens with lobaric acid in eNA is about 16%, considerably less than in Europe.

Distribution: (map based on 217 sites: CUP, DUKE, HINDS, LAY, MAINE, MIN, NY, US, Crowe 1994, Dey 1978, Gowan & Brodo 1988, Harris et al. 1988, Thomson 1984 [Canada only], Wong & Brodo 1992): P. saxatilis is common in boreal and arctic regions of the Northern Hemisphere and is also found in South America, Africa, and New Zealand; in eNA it has a distribution like P. omphal- odes but has been found slightly farther south, in Wisconsin (MIN), southern Ontario (Wong & Brodo 1992), eastern Massachusetts (MIN, LAY), and Long Island (NY).

Remarks: Morphologically, P. saxatilis closely resembles P. pseudosulcata Gyelnik of the Pacific Northwest (=P. kerguelensis auct., not A. Wilson), but the latter is said to have more closely appressed, less overlapping lobes and more frequently forked rhizines (Goward et al. 1994). It differs more clearly in its chemistry, having salazinic acid instead of protocetraric acid.

Parmelia squarrosa Hale, Phytologia 22: 29 (1971). Type collection (Hale 1987): USA, Virginia, Shenandoah National Park (US, Hale 36494, holotype).

Morphology: Thallus adnate to loosely adnate on trees, less commonly on rocks, rarely on moss (LAY, US), greenish to whitish mineral gray, with divaricate, contiguous, or imbricate lobes 1-5 mm wide. Upper surface plane to foveolate with laminal and marginal pseudocyphellae often forming a reticulate network; isidia cylindrical, up to 0.5 mm tall and becoming dense in the older, central part of the thallus. Rhizines squarrosely branched (simple at the lobe margins). Pycnidia and apothecia uncommon; spores 13-15 x 8-9 mm.

Chemistry: Medulla contains salazinic and consalazinic acid (K+ yellow changing to red, P+ orange); lobaric acid has not been reported.

Distribution: (map based on 909 sites: CUP, DIRIG, DUKE, HINDS, LADD, LAY, MAINE, MIN, NY, NYS, SCHMITT, US, Crowe 1994, Dey 1978, Flenniken & Showman 1990, Gowan & Brodo 1988, Harris 1988, Harris et al. 1988, Ladd 1991, Selva 1988, 1989, Thomson 1984 [Canada only], Wetmore 1988, Wilhelm 1995, Wong & Brodo 1992): P. squarrosa is common in eNA, especially in the Great Lakes-Appalachian region and is also found in eastern Asia and rarely in western Europe (Hyvönen 1985) and western NA. It has a more southern, temperate distribution than P. saxatilis, extending south to Arkansas, Alabama, and South Carolina, but overlaps with P. saxatilis from the Great Lakes through New York and New England to Quebec and Newfoundland. In the southern Appalachians the range of P. squarrosa extends into the lower foothills, unlike P. saxatilis, and generally P. sulcata, which are restricted to the high mountain areas.

Remarks: P. squarrosa can generally be clearly distinguished from P. saxatilis by its squarrosely branched rhizines (simple and furcately branched in P. saxatilis). With very small specimens, however, or specimens where the rhizines are not well developed (Dey 1978), identification may be more difficult and require scraping of the lower surface with a scalpel or razor blade to detach the rhizines onto white paper to visualize them clearly.

Parmelia sulcata Taylor, in Mackay, Flora Hibernica: 145 (1836). Type collection (Hale 1987): Ireland (FH, lectotype); Syn: P. rosiformis (Ach.) Gyelnik.

Morphology: Thallus adnate to loosely adnate on trees and rock, rarely on soil (DIRIG; Sirois et al. 1988), greenish to whitish mineral gray, with divaricate to imbricate lobes 1-5 mm wide. Upper surface plane to foveolate with laminal and marginal pseudocyphellae; soralia laminal and marginal, circular to elongate, eroding, containing granular soredia. Rhizines simple to squar-rosely branched. Pycnidia and apothecia rare; spores 11-14 x 6-8 m m.

Chemistry: Medulla contains salazinic and consalazinic acid (K+ yellow changing to red, P+ orange); also acces-sory lobaric acid in specimens from southern Appalachian mountains. (Dey 1978).

Distribution: (map based on 1449 sites: CUP, DIRIG, DUKE, HINDS, LADD, LAY, MAINE, MIN, NY, US, Ahti 1964, Ahti & Jørgensen 1971, Brodo 1967, 1968, Crichton 1994, Dey 1978, Evans & Meyrowitz 1926, Giardini 1922, Gowan & Brodo 1988, Harris et al. 1988, Hedrick 1940, Henry & Hampton 1974, Hyerczyk 1996; Ladd et al. 1994, Lamb 1954, LeBlanc & De Sloover 1970, LeGallo 1952, McCune 1988, McQueen 1988, Merrill 1926, Mozingo 1948, Newberry 1974, Nimis 1985, Rao & LeBlanc 1967, Reilly 1972, Selva 1988, 1989, Sirois et al. 1988, Taylor 1967, Thomson 1984 [Canada only], Thomson & Weber 1992, Wilhelm 1995, Will-Wolf 1980, Wong & Brodo 1992): P. sulcata is an abundant worldwide species found on all continents; in eNA it is common in the Great Lakes-Appalachian region northward and also the Midwest region from Ohio to northern Iowa and southern Minnesota. It has also been reported from central Missouri (Ladd et al. 1994), but unlike P. squarrosa, not from the Ozark Plateau region, or the southern Appalachian foothills of Tennessee, Alabama, Georgia, or South Carolina.

Remarks: P. sulcata is an abundant, even weedy, species that more often than the other Parmelia species of eNA can be found in highly disturbed sites, such as extensive agricultural lands.


The author would like to express his sincere thanks to Patricia Hinds for photography; to Paula DePriest and Clifford Wetmore for making available computer lists of the US and MIN collections of Parmelia, respectively; to Christopher Campbell, Elisabeth Lay, and Donald Pfister for making collections available at MAINE, LAY, and FH, respectively; to Clifford Wetmore (MIN) and Pak Wong (CANL) for lending specimens, and to Irwin Brodo, Stephen Clayden, Paula DePriest, Richard Harris, Claire Schmitt, and Clifford Wetmore for checking specimens. I am also indebted to Christopher Hinds for computer help and to Irwin Brodo, Robert Dirig, Richard Harris, and Patricia Hinds for reviewing drafts of the manuscript.

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