BFNA Title: Plagiochilaceae
Author: R. H. Zander

Date: August 4, 2022
Edit Level: S
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
BFNA Web site: http://www.mobot.org/plantscience/BFNA/bfnamenu.htm

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50. PLAGIOCHILACEAE Müll. Frib.

Richard H. Zander

Plants arching or trailing from naked rhizomes, or forming mats. Branching intercalary, from leaf axils; usually without flagella. Leaves alternate, succubous, plane, dorsal margin often reflexed, simple or 2-lobed, often spinose-dentate; underleaves vestigial or absent, simple or laciniate. Rhizoids confined to rhizomes where they are scattered over ventral stem. Propagula elongate, with conspicuous scale leaves sometimes present on leaf surfaces, or with asexual reproduction by fragmenting leaves. Gynoecium terminal on an ordinary leafy branch, with or without subfloral branching. Perianth well developed, dorsiventrally flattened, mouth wide. Perigynium absent.

Genera 9 (2 in the flora), species 400–450 (26 + 1 in the flora). Cosmopolitan, except Antarctica.

The Plagiochilaceae is a large, widespread family characterized by perianths laterally compressed, bilabiate, and wide-mouthed; sex organs not in specialized positions; capsule walls many-stratose; and seta thick (R. M. Schuster 1980: 328).

SELECTED REFERENCES  Groth, H., M. Lindner and J. Heinrichs. 2004. Phylogeny and biogeography of Plagiochila (Plagiochilaceae) based on nuclear and chloroplast DNA sequences. Monogr. Syst. Bot. Missouri Bot. Gard. 98: 365--387. Heinrichs, J. 2006. Molecular phylogeny and biogeography of Plagiochila (Jungermanniidae: Plagiochilaceae). Plant Genome: Biodiversity and Evolution, Vol. 2B, pp. 433--458. Science Publ. Heinrichs, J., M. Lindner and H. Groth. 2004. Sectional classification of the North American Plagiochila (Hepaticae, Plagiochilaceae). Bryologist 107: 489--496. Hong. W. S. 1992. Plagiochila in Western North America. Bryologist 95: 142--147. Schuster, R. M. 1959a. A monograph of the Nearctic Plagiochilaceae. Part 1. Introduction and Sectio 1. Asplenioides. Amer. Midl. Nat. 62: 1--166. Schuster, R. M. 1959b. Part 2. Sectio Zonatae through Sectio Parallelae. Amer. Midl. Nat. 62: 257--395. A monograph of the Nearctic Plagiochilaceae. R. M. 1960. A monograph of the Nearctic Plagiochilaceae. Part 3. Sectio Coniguae to conclusion. Amer. Midl. Nat. 63: 1--130. Schuster, R. M. 1980. The Hepaticae and Anthocerotae of North America East of the Hundredth Meridian. Volume IV. Columbia University Press, New York. M. L. So. 2001. Plagiochila (Hepaticae, Plagiochilaceae) in China. Bryologist 60: 1--214. Stotler, R. E. and B. Crandall-Statler. 2017. A synopsis of the liverwort flora of North America north of Mexico. Ann. Missouri Bot. Gard. 102: 574--709.

1. Leaves not inserted to the mid line of the stem, not decurrent; autoicous ... 1. Pedinophyllum, p.

1. Leaves inserted to the mid line of the stem, usually decurrent; dioicous ... 2. Plagiochila, p.

1. PEDINOPHYLLUM Lindberg, Hepat. Hibern., 504. 1875 * .[Greek pedino-, flat, and phyllum, leaf, alluding to the plane leaves]

Dale H. Vitt

Plants prostrate to suberect, in loose mats, medium-sized, pale brown to yellow-green. Stems homogenous in transverse section. Leaves somewhat antically secund, not inserted to the stem mid-line, not or only slightly decurrent, quadrate to oblong to oblong-ovate, apex broadly rounded-truncate, retuse; margins plane and entire. Underleaves minute, filiform. Oil bodies 2--6(--8) per cell, 5--8 x 5--16 /um, granular. Specialized structures for asexual reproduction absent. Sexual condition autoicous. Androecial bract margins entire. Female bract margins usually entire. Perianth oblong to obovate.

Species 3 (1 in the flora): North America, c,s Europe, Asia, n Africa.

Pedinophyllum is a genus of three species, with one in North America.

1. Pedinophyllum interruptum (Nees) Kaalaas, Nyt Mag. Naturvidensk. 33(1--2): 190. 1892

Jungermannia interrupta Nees, Naturgesch. Eur. Leberm. 1: 165. 1833

Plants to 4 cm in length, about 1--3(--4) mm wide. Leaves 1.3 x 1.6 mm, as long or longer than wide. Leaf cells 22--30 x 23--38 /um, walls thin, with trigones variably absent to minute.

On thin soil over rock surfaces, also on logs, most frequent in white cedar swamps. Conn., Mass., Mo., Ohio; Eurasia.

Pedinophyllum interruptum is distinguished from species of Plagiochila, when fertile, by the autoicous inflorescences and entire female bracts. When sterile, the leaves not inserted all the way to the stem mid-line, non-decurrent, and vary around a quadrate shape. Pedinophyllum bears some resemblance to species of Chiloscyphus and Lophocolea, but it differs in having minute, filiform underleaves and rhizoids continuously present along the stem, rather than restricted to the bases of well-developed underleaves as in species of the former genera.

2. PLAGIOCHILA (Dumortier) Dumortier, nom. cons., Recueil. Observ. Jungerm., 14. 1835 * [From plagio-, oblique, slanting, and cheilos, edge, Greek, alluding to asymmetric leaves]

Radula sect. Plagiochila Dumortier, Syll. Jungerm. Europ., 42. 1831

Richard H. Zander

Plants medium to large-sized, green to brownish green, with creeping stolons. Stems in transverse section with differentiated cortical cells with slightly to moderately thickened walls. Leaves spreading, sometimes postically secund but rarely antically secund, inserted to the mid line, mostly weakly to strongly decurrent antically and postically, ovate or obovate to orbicular or ovate-rectangular, commonly asymmetric, apex usually entire, occasionally retuse or 2-lobed; margins usually reflexed antically, edentate or more usually with teeth, teeth linear to triangular. Underleaves small or vestigial, often with broadened bases. Oil bodies 4--20 per cell, usually botryoidal, composed of globules, or granular. Specialized structures for asexual reproduction present or absent. Androecial bracts with dorsal margins with simple slime papillae or with 2- to 5-celled filaments ending with slime papillae. Female bract margins dentate. Perianth cylindric or campanulate.

Species ca. 400 (26 in the flora): Greenland, North America; Mexico; West Indies; Central America; South America; Eurasia; Africa; Atlantic Islands; Indian Ocean Islands; Pacific Islands (including Hawaii and New Zealand); Australia.

Plagiochila species may be recognized by leaves succubous, asymmetrically ovate or tapering-rectangular, commonly dentate or ciliate but seldom bilobed, underleaves small, median laminal cells often collenchymatous, often with strongly bulging trigones, cells with several oil bodies per cell.

The present work is based on extensive and detailed taxonomic treatments of W. S. Hong (1992), R. M. Schuster (1959 a,b, 1960, 1980), R. E. Stotler and B. Crandall-Stotler (2017), and M. L. So (2001). Much analysis, both classical and phylogenetic has been done by H. M. Groth, J. Heinrichs and colleagues (e.g. H. M. Groth and J. Heinrichs 2004; J. Heinrichs 2006; J. Heinrichs et al. 2004.) largely for the Neotropics. The species recognized, however, are those of R. E. Stotle3r and B. Crandall-Stotler (2017).

Some technical language is necessary. Antical refers to the uppermost side of a prostrate liverwort, such as the antical stem surface. The opposite, postical, refers to the lowermost part of the plant. The leaves of Plagiochila are succubus, meaning that if an erect ancestor were to fall prostrate and the leaves flatten against the substrate, the upper edge of all the leaves would lean backwards towards the base of the plant. Thus, the leaf is usually bent so the upper, adaxial surface faces upwards. In Plagiochila, antical means the leaf edge above an imbricated leaf. Likewise, the abaxial side of the leaf faces down, and is the postical surface.

A vitta (vitta, Lat., a fillet) is a median band or ribbon of longitudinally elongate cells at the base of a leaf. A cnemis is a lengthwise fold in the leaf bulging upwards and looking like a shin (cnemis, Gk., a shin). Intercalary branches originate below the stem epidermis and have a collar at their base.  Terminal branches replace half of a leaf.

SELECTED REFERENCES Frye, T. C. and L. Clark. 1945. Hepaticae of North America. Part III. Univ. Wash. Publ. Biol. 6: [i]–iii, 337–564. Hicks, M. L. 1992. Guide to the Liverworts of North Carolina. Duke University, Durham and London. Stotler, R. E. and B. J. Crandall-Stotler. 2017. A synopsis of the liverwort flora of North America north of Mexico. Ann. Missouri Bot. Gard. 102(4): 574–709. Steere, W. C. and H. Inoue. 1978. The hepaticae of arctic Alaska. J, Hattori Bot. Lab. 44: 251--345.

1. Leaves or distal portions caducous or fragmenting, at least in some plants; cells medium-sized 18--25 \um wide.

2. Leaves ovate-triangular to ovate-falcate, widest just above the long-decurrent antical base; postical portion above base obviously arched and dilated; distal halves of leaves irregularly caducous; branching at least in part terminal......... 1. Plagiochila appalachiana

2. Leaves widest near to above mid leaf or rectangular; narrow near base, with postical margin not dilated basally, leaves short-decurrent antically; variously caducous; branching all intercalary.

3. Leaves obdeltoid and deeply palmately divided into linear lobes, which are caducous and fragment leaving irregular, truncate stubs  6. Plagiochila caduciloba

3. Leaves always caducous at base, with ordinary sharp or triangular lobes and/or teeth.

4. Small, plants to 1.5 mm wide; leaves when mature edentate or with 1--3 large teeth.

5. Leaves oblong, 2--3-lobed, usually edentate but sometimes with 1--4 additional small teeth ................................................. 9. Plagiochila exigua

5. Leaves of weak shoots 2-lobed, but robust shoots with leaves obovate, weakly 2-lobed or unlobed, with 3--8(--15) teeth 19. Plagiochila punctata

4. Larger, plants (1.3--)1.5--2.4(--2.5) mm wide; leaves when mature with 3--9 or more large teeth.  

6. Leaves oblong, mostly more than twice as long as wide; teeth lobe-like and coarse[AW1] ; leaves often with apex divided into 2 primary lobes ....................... ....................................................................................................................... ................................................................................... 5. Plagiochila austinii

6. Leaves obovate, normally averaging less than twice as long as wide; teeth narrow, usually spinose or finely spinose; leaves never with clear indication of 2-lobing .......................................................... 24. Plagiochila sullivantii

1. Leaves all persistent, not fragmenting; asexual reproduction by propagula or absent.

7. Middle of leaf base with a vitta of elongate cells; apical cells small, ca. 16--18(--20) \um wide or less; leaves ovate to ovate-triangular, with numerous spinose teeth; plants usually +/- bronzed, with at least stem brownish; propagula absent.

8. Leaves with fine marginal teeth of 2--4(--5) cells in length; apical cells 17--20 \um wide; cells of vitta with +/- strong trigones, 17--24 \um wide .............................. ................................................................................................................................. ......................................................................................... 21. Plagiochila retrorsa

8. Leaves with coarser marginal teeth, 3--6(--10) cells in length; apical cells usually 14--17 \um wide; cells of vitta +/- equally thick-walled, 13--16(--18) \um wide . ................................................................................................................................. ............................................................................... 23. Plagiochila semidecurrens

7. Cells in middle of leaf base not strongly elongate, not much differentiated from surrounding leaf cells (i.e., not vittate[AW2] ); apical cells (17--)18--40 \um x 22--40 \um, plants usually green.

9. Median and apical cells averaging 25--40 \um wide; leaves entire or with 4--35 teeth, teeth short and fine to ciliate or spinose, always slender-based; branches normally all intercalary (arising from leaf axils, with a basal collar); asexual reproduction absent.

10. Leaf margins always with 4--12(--15) long, spinose to finely spinose teeth each terminating in a row of (3--)4--6 strongly elongate cells; leaves oblong-ovate to subrectangular, 1.2--2.3 x as long as wide; plants strongly shiny, with delicate, patent leaves.

11. Leaves broad, ovate to ovate-oblong, ca. 1.2--1.5:1, the apices often conspicuously 2-lobed, with acuminate lobes ........ 8. Plagiochila echinata

11. Leaves narrow, oblong to rectangular, 1.5--2:1, the rounded or subtruncate leaf apices not or hardly 2-lobed .................................................................. ....................................................................................................................... .............................................................................. 22. Plagiochila sciophila

10. Leaf margins entire to dentate with (15--)20--35 short, fine teeth; leaves short- to quadrate-ovate to suborbicular, usually (0.8--)1--1.4 x as long as wide; plants nearly or quite dull.

12. Median cells large, 33--42 \um wide.

13. Leaves usually provided with a few irregular teeth, at apex often broadly truncate or trancate-2-lobed; occasional underleaves laminate. ................................................................... 7. Plagiochila columbiana

13. Leaves usually rounded apically, entire-margined or with scattered fine, regular teeth; underleaves always vestigial, of 2--several cilia 2. Plagiochila arctica

12. Median cells small, 18--32(--36) \um.

14. Base of leaf lacking all indication of vittae; leaves entire-margined to dentate, antical margin moderately to slightly reflexed ..................... ............................................................................................................. ................................................................. 4. Plagiochila asplenioides

14. Base of leaf sometimes with slight development of a vitta; leaves always dentate, antical margin broadly reflexed for nearly entire length;

15. Cortex 2--3 cells thick; perianth mouth ciliate; leaf margins with a few irregular teeth ................................ 16. Plagiochila ovalifolia

15.  Cortex 3--5 cells thick; perianth mouth dentate; leaf margins entire to dentate with (15--)20--36 short, fine teeth........................ ......................................................................................................... ............................................................ 18. Plagiochila porelloides

9. Median and apical cells averaging (17--)18--25(--28) \um wide; margins with a limited number (5--16) of coarse teeth, these sometimes vestigial and never finely spinose, the larger (at least) broad-based; branches terminal or intercalary, asexual propagules present or absent.

16. Branches infrequent, lateral-intercalary (arising from leaf axils, with a basal collar); propagula unknown; leaves usually 1.5--1.8 x as long as wide ...... 11. Plagiochila gracilis

16. Branches largely terminal (replacing ventral half of a leaf) on mature plants (but intercalary branches produced as a response to damage); plants reproducing occasionally by propagula; leaves usually more than 1.8 x as long as wide.

17. Leaves imbricate, the strongly broadened postical bases shingled, +/- completely hiding stem in postical aspect; dilated postical leaf bases long- or short-decurrent but always +/- erect, collectively forming an erect crest or convolute and forming water-sacs; underleaves distinct to comparatively large.

18. Leaves short-decurrent postically; whole [AW3] postical leaf margin sharply spinose-dentate, including the somewhat cristate basal region; underleaf essentially a ciliate-margined lamella ........... 15. Plagiochila montagnei

18. Leaves long-decurrent postically; either basal or distal portions virtually or quite edentate; underleaf deeply divided into laciniae or cilia.

19. Postical leaf margin of sterile shoots strongly crispate-undulate; otherwise leaf margins entire or virtually so (except for 1--several low teeth near apex); propagula rare or absent ..... 25. Plagiochila undata

19. Postical leaf margin of sterile shoots not or obscurely undulate, usually distinctly spinose-dentate (either near leaf apex or near base or both); almost always with propagula.

20. Postical leaf bases dilated, reflexed and convolute, forming a tubular water-sac of thick-walled, scarcely elongated cells, usually bearing 2--6 spinose teeth; leaf apices entire to weakly dentate; antical keel of perianth 2--4-dentate; underleaves of 2--several linear, largely 1-seriate cilia ........... 14. Plagiochila miradorensis

20. Postical leaf bases narrow, erect, forming a crista, edentate (rarely with 1--2 teeth); leaf apices dentate; antical keel of perianth edentate; underleaves of 2-several slender laciniae or lanceolate lobes.

21. Leaves (of mature shoot sectors) +/- sharply spinose-dentate, usually with 2--3(--5) coarse apical teeth; postical margins usually with 5--10 less coarse teeth; trigones generally strongly bulging........................................................................................ .................................................................................................... ........................................................... 20. Plagiochila raddiana

21. Leaves (of mature shoot sectors) subentire or entire, usually with 2--4 low, obtuse teeth at apex; postical margins entire or obsoletely 1--2-dentate; trigones often weak

.... ................................................................ 12. Plagiochila invisa

17. Leaves approximate to laxly imbricate, rectangular to ovate; postical bases not densely shingled (leaving the stem conspicuously exposed in postical view), short-decurrent, the decurrent strip flat or at most narrowly erect; underleaves minute or obsolete, never of laciniae or lamellae.

22. Leaves short- to quadrate-rectangular, broadly subtruncate at apex, 1.1--1.3 x as long as wide, with small irregular teeth confined to near apex; cells +/- equally thick-walled [AW4] and trigones minute.................................. .................................................................................................................. .................................................................... 3. Plagiochila aspleniformis

22. Leaves either ovate (and widest just above base) or narrowly rectangular, usually at least 1.3 x as long as wide; marginal teeth large, distinct; cells collenchymatous (except in shade forms), median cells always with thin walls (unless the bulging trigones are confluent).

23. Leaves lingulate-rectangular, 2--2.5(--3) x as long as wide, parallel-sided, the postical base neither dilated nor arched; leaves distinctly bordered with 1--2 rows of elongate cells (whose tangential walls are strongly thick to form a border), distant; leaves spreading at 65--75 °., in drying tubular-involute; teeth of leaves few and low, largely at the rounded, truncate apex; propagula on postical leaf surface only .. 13. Plagiochila micropteryx

23. Leaves +/- ovate, 1--1.3 x as long as wide; postical base slightly to strongly dilated and arched; greatest width of flattened leaf thus subbasal; leaves not distinctly bordered (the marginal cells not set off as a border, rarely extremely elongate); leaves typically slightly imbricate to approximate, not involute in drying; propagule position various.

24. Mature moist shoots with leaves spreading at 55--75 ° from stem apex, typically (1--)1.3--1.8 x as long as wide when flattened, the postical base conspicuously dilated; propagula confined to postical leaf surface ............................................ 26. Plagiochila virginica

24. Moist shoots, at least distally, with leaves suberect, spreading at 40--50 ° (on older portions sometimes at 55--70 °); mature leaves 1.9--2.4 x as long as wide when flattened, the postical base barely or weakly dilated, thus almost subrectangular or narrowly ovate; propagula usually in part on adaxial (antical) leaf faces.

25. Mature, robust stems with somewhat ovate leaves whose postical bases are somewhat broadened; postical leaf margins, above broadened base, nearly (but usually not quite) at right angles to stem; leaves with teeth small to weakly spinose; perianth mouth with usually relatively low, inconspicuous teeth .................................................................................................... .................................................................................................... ................................................................ 17. Plagiochila patula

25. Mature, robust stems with rectangular leaves; postical leaf bases not or hardly broadened, and postical margins above leaf bases clearly erect-spreading; leaves always sharply, often spinose-dentate; perianth mouth with crowded cilia or narrow laciniae ............................................... 10. Plagiochla floridana

1. Plagiochila appalachiana Inoue, J. Hattori Bot. Lab. 40: 415. 1976. E

Plagiochila yokogurensis Stephani subsp. fragilifolia R. M. Schuster, J. Hattori Bot. Lab. 18: 18. 1957.

Plants green to yellowish green, large, 2.8--3.8 mm wide. Branching at least in part terminal and pseudodichotomous Leaves spreading at 85--90 °, weakly to moderately imbricate, mature leaves strongly falcate, distal halves of leaves irregularly caducous, in shape ovate-triangular to ovate-falcate, widest just above the base, postical portion above base arched and moderately dilated, 1.5--2 x as long as wide, antical base long-decurrent, postical base short-decurrent, vitta absent; margins coarsely 2--3(--4) dentate, postical margin with additional 2--8 smaller teeth; median cell width 17--25 \um, cells thin-walled, trigones small with concave walls; apical cells 24--28 \um wide. Oil bodies ellipsoidal, botryoidal, papillose-segmented. Underleaves minute to small, lanceolate, 5--6 cells in length or of 2--3 celled uniseriate cilia. Propagula absent.

Gorges and ravines, vertical acid rock faces, along streams, occasionally calcareous rock, soil at tree bases, tree trunks; 50--300 m elevation; Ala., D.C., N.C., S.C., Va.

When Inoue (1976) treated Plagiochila yokogurensis Stephani subsp. fragilifolia R. M. Schuster at the species level, he created P. appalachiana as a replacement name because of the blocking name P. fragilifolia Pearson. The east Asian Plagiochila parvifolia Lindenberg (=P. yokogurensis subsp. yokogurensis) has not been reported for the flora. Among the caducous species of Plagiochila, the leaves broadest at the base immediately distinguish P. appalachiana. Plagiochila appalachiana is restricted to the eastern United States from Virginia to South Carolina, occurring largely in the western Appalachians, but also in the Great Dismal Swamp of Virginia near the Atlantic coast.

2. Plagiochila arctica Bryhn & Kaalaas var. arctica, Rep. Second Norweg. Arctic Exped. 11: 41. 1906, as autonym generated by var. intermedia

Plagiochila asplenioides (L.) Dumort. subsp. arctica (Bryhn & Kaal.) R. M. Schuster; P. arctica var. intermedia R. M. Schuster, Amer. Midl. Naturalist 62: 152. 1959

Plants usually dull green, small, 1.3--1.8(--2) mm wide. Branching normally all intercalary (from leaf axils). Leaves imbricate, spreading at 45 ° or more, persistent, not fragmenting, reniform to suborbicular, usually 0.8--1 x as long as wide, usually rounded apically, short-decurrent antically, vitta absent; margins entire or occasionally with a few short teeth; median cells 34--38 \um wide, cell walls thin to slightly thickened, trigones small to moderate in size, not bulging; apical cells large, (17--)18--40 x 22--40 \um. Oil bodies botryoidal. Underleaves always vestigial, of 2--several cilia. Propagula absent.

Silt, soil, rock, copper mine, north-facing cliffs, steep wet slopes, damp humus over calcareous clay-shale; 50--3700 m; Greenland; B.C., Nun., N.W.T., Que., Yukon; Alaska, Colo.; n Eurasia.

The Colorado specimen of Plagiochila arctica was collected by N. G. Miller on Mt. Evans.

3. Plagiochila aspleniformis R. M. Schuster, Amer. Midl. Naturalist 63: 51. 1960  E

Plants usually green, large to very large, 3.5--5.5 mm wide. Branching most or all terminal on mature plants. Leaves with postical bases not densely shingled (stem is quite exposed in postical view), approximate to laxly imbricate, persistent, not fragmenting, postical bases short-decurrent. Leaves short- to quadrate-rectangular, broadly subtruncate at apex, 1.1--1.3 x as long as wide, short-decurrent, the decurrent strip flat or at most narrowly erect, vitta absent; margins with small irregular teeth confined to near apex; median cells averaging (17--)18--25(--28) \um wide; cells equally thick-walled (thicker on margins), with minute trigones; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies coarsely segmented. Underleaves minute or obsolete, never of laciniae or lamellae. Propagula n distal postical surface of leaves.

Sandy soil, sand, limestone, Magnolia trunk, base of Quercus, hammock, riverbank; 50--100 m; Fla., N.C., N.Y.; Central America (Guatemala); South America (Suriname).

Plagiochila aspleniformis is similar to P. asplenioides in the large plant size (to 5.5 mm in width), and somewhat distant, ovate-rectangular to oblong leaves. It differs in dry plants shiny, marginal teeth reduced and few event in robust plants, terminal branching, abundant propagula on postical leaves, and smaller, evenly thick-walled laminal cells.

4. Plagiochila asplenioides (Linnaeus) Dumortier, Recueil Observ. Jungerm., 14. 1835 Jungermannia asplenioides Linnaeus, Sp. Pl. 2: 1131. 1753

Plants usually dull green, large to very large, 2--7 mm wide. Branching normally all intercalary (from leaf axils). Leaves laterally spreading, occasionally postically secund, persistent, not fragmenting, short- to quadrate-ovate to suborbicular, variable in shape, usually (0.8--)1--1.4 x as long as wide, antical margin moderately to slightly reflexed, short-decurrent postically and moderately decurrent antically, vitta absent; margins entire to dentate with (15--)20--35 short, fine teeth, entire-margined to dentate; median cells small, 18--36 \um wide, cell walls thin-walled, trigones present, concave to somewhat bulging; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies botryoidal. Underleaves minute, filiform to 2--4-fid and ciliate. Propagula absent.

[AW5] 

Rock, soil; low to high elevations; Alta., B.C., N.W.T.; Alaska, Idaho, Wash.; Europe.

Plagiochila asplenioides and P. porelloides were confused until recently, and almost all records of P. asplenioides may be P. porelloides.  The range of P. asplenioides is currently uncertain and needs to be checked carefully.

5. Plagiochila austinii A. Evans, Rhodora 16: 68. 1914, as “austini” E

Plants deep green to brownish, large, (1.3--)1.5--2.4(--2.5) mm. Branching all intercalary. Leaves distant to slightly overlapping, wide spreading, caducous at base, oblong, mostly more than twice as long as wide, apex often divided into 2 primary lobes, narrow near base, with postical margin not dilated basally, 2--2.4 x as long as wide, short-decurrent antically, vitta absent; margins with 3--9 or more sharp teeth, these never finely spinose; median cell width 18--25 \um, cell walls weakly collenchymatous, trigones small or rarely large and concave; apical cells 13--15 \um wide. Oil bodies botryoidal. Underleaves small, of 1--3(--4) short cilia. Propagula absent.

Rock, vertical crevices in limestone, sandstone, conglomerate boulder, shaded damp boulders and ledges, vertical granite face, near stream; 765--1800 m; N.S.; Conn., Ky., Mass., N.H., N.C., N.Y., Ohio, Pa., S.C., Tenn., Vt., W.Va., Va., Wisc.

Plagiochila austinii is largely Appalachian in geographic range. It has elongate leaves, commonly with two enlarged teeth apically, in addition to a very few smaller denticulations.

6. Plagiochila caduciloba H. L. Blomquist, Bryologist 42: 114. 1939 E

Plants dull olive-green to brownish, small, 0.8--1.8(--2) mm wide. Branching usually simple, intercalary. Leaves distant to approximate, divergent, caducous and fragmenting to an irregular truncate stub, obovate to obdeltoid, dorsally convex, deeply palmately divided into irregular linear lobes, narrow near base, with postical margin not dilated basally, 1.2--1.4 x as long as wide, short-decurrent antically, vitta absent; margins edentate or with 1--3 teeth, occasionally a tooth ending a fragmentary lobe; median cells 20--25 x 32--42 \um wide, cell walls collenchymatous, walls thickened, trigones bulging; apical cells 21--25 \um wide. Oil bodies smooth, homogeneous. Underleaves minute, subulate. Propagula absent.

Shady, damp rock walls, occasionally on bark, near waterfalls and cascades; 610--1830 m elevation; Ga., Ky., N.C., S.C., Tenn.

The leaves of Plagiochila caduciloba split into squared-off branching, then fragment into irregular many-celled plates which are easily dispersed, and establish new colonies in suitable habitats.

7. Plagiochila columbiana A. Evans, Bot. Gaz. 21: 189. 1896 C E

Plants usually dull green, large, 3.5--4 mm wide. Branching normally all intercalary (from leaf axils). Leaves widely divergent, contiguous to slightly imbricate, persistent, not fragmenting, short- to quadrate-ovate to suborbicular, usually (0.8--)1--1.4 x as long as wide, at apex often broadly truncate or trancate-2-lobed, antically short-decurrent, postically very short-decurrent, vitta absent; margins with a few irregular teeth; median cells 34--38 \um wide, cell walls thin- to moderately thick-walled, trigones present, concave; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies botryoidal. Underleaves distinct, lamellate. Propagula absent.

Bark, soil, rock ledges, riverside, swamp forest; 20--1300 m; Fla., D.C., N.C.

Plangiochila columbiana is distinguished from related species by the almost entire leaves, large leaf cells and often relatively large underleaves. It is closely related to P. porelloides.

8. Plagiochila echinata R. M. Schuster, Amer. Midl. Naturalist 62: 341. 1959 C E

Plagiochila euryphyllon Carl ex Herzog subsp. echinata (R. M. Schuster) Inoue

Plants usually shiny green, large, 2.8--3.5 mm wide. Branching normally all intercalary (from leaf axils). Leaves patent, weakly to moderately imbricate, persistent, not fragmenting, broad, ovate to ovate-oblong, the apices often conspicuously 2-lobed, lobes acuminate, postical margin above base conspicuously broadened, 1.2--1.5 x as long as wide, antical and postical margins short-decurrent, vitta absent; margins varying from entire to finely and copiously dentate, to ciliate with finely spinose teeth, teeth always slender-based; median cells averaging 25--40 \um wide, cell walls weakly collenchymatous, trigones present, concave, weak; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies of minute spherules. Underleaves minute, of 2--4 short cilia. Propagula absent.

Sandstone boulders, occasionally siliceous rock, gorge, near waterfall, streamside, forested ravine; 300--1300 m; Ky., N.C., S.C., Tenn.

9. Plagiochila exigua (Taylor) Taylor, London J. Bot. 5: 265. 1846

Jungermannia exigua Taylor, Trans. Bot. Soc. Edinburgh 1: 179. 1843 (1844)

Plants pale to olive-green small, 1.1--1.3 mm wide. Branching all intercalary. Leaves remote to approximate, wide-spreading, caducous at base, oblong, 2--3 lobed, with lobes triangular, widest near to above mid leaf or rectangular, narrow near base, postical margin not dilated basally, about 3 x as long as wide, leaves short-decurrent antically, vitta absent; margins usually edentate but sometimes with 1--4 additional small teeth; median cells 18--25 \um wide, cell walls collenchymatous, trigones weak and concave to bulging; apical cells 17--20 \um wide. Oil bodies homogeneous. Underleaves very small, subulate to filiform. Propagula absent.

Tree trunks, Abies fraseri, moist rocky soil, Spruce-Fir zone, near mountain summit; 1700--2000 m; N.C., Tenn., Va.; Mexico; West Indies; South America; Eurasia; Africa; Atlantic Islands.

The name P. corniculata (Dumortier) Dumortier has been widely (but incorrectly) applied to this species.

10. Plagiochila floridana A. Evans, Bot. Gaz. 21: 190. 1896 C E

Plants usually green, large, 2.5--3 mm wide. Branching largely terminal on mature plants. Leaves erect-spreading (40--50 °), postical bases not densely shingled (leaving the stem distinctly exposed in postical view), typically slightly imbricate to approximate, not convolute in drying, persistent, not fragmenting, +/- ovate to rectangular, postical base slightly to strongly dilated and arched, leaf widest near base, leaves not distinctly bordered (marginal cells rarely extremely elongate), mature leaves 1.9--2.4 x as long as wide when flattened, postical leaf bases not or hardly broadened, and erect-spreading, short-decurrent, the decurrent strip flat or at most narrowly erect, vitta absent; margins with a limited number (5--16) of coarse teeth, the larger broad-based, always sharply, often spinose-dentate; median cells averaging (17--)18--25(--28) \um wide, cell walls collenchymatous (except in shade forms), median cells always with thin walls and bulging trigones; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies segmented. Underleaves minute or obsolete, never of laciniae or lamellae. Propagula usually in part on antical leaf faces.

Decaying wood, bark, base of hardwood trees, Quercus virginiana, shady rock, hammock, vertical sandstone near falls; 0—80 m; Fla., Ga., La., Miss.

Plagiochila floridana is distinguished largely by the imbricate, oblong-ligulate leaves, short-decurrent postical and antical leaf bases, and propagula formed on both leaf faces. The perianth mouth is crowded with cilia or narrow laciniae.

11. Plagiochila gracilis Lindenberg & Gottsche in G. M. Gottsche, J. B. W. Lindenberg & C. G. D. Nees, Syn. Hepat., 632. 1847

Plagiochila schofieldiana Inoue

Plants usually green, large, 2--3 mm wide. Branching infrequent, lateral-intercalary. Leaves laterally patent, oblique to horizontally spreading, persistent, not fragmenting, oblong-ovate, asymmetrically 2-lobed, postical margin arched, usually 1.3--1.8 x as long as wide, antically moderately decurrent, postically weakly decurrent, vitta absent; margins with a limited number (5--16) of coarse teeth, these sometimes vestigial and never finely spinose, the larger (at least) broad-based; median cells averaging (17--)18--25(--28) \um wide, cell walls collenchymatous, trigones moderate in size to large; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies finely granular. Underleaves vestigial. Propagula unknown.

Trunks of Cupressus nootkatensis, shaded humid base of cliff; B.C.; 0—100 m; B.C.; Alaska (Attu I., Moresby I.); e Asia.

Plagiochila gracilis has bidentate leaves usually 1.2--1.8 x as long as wide, with (2--)5--9(--18) needle-like marginal teeth. It was originally collected in our floral area as P. schofieldiana at Bigsby Inlet, SE Moresby Island, Queen Charlotte Islands, and is a hyperoceanic species.

12. Plagiochila invisa (R. M. Schuster) R. M. Schuster, Hepat. Anthocerotae N. Amer. 4: 513. 1980 C E

Plagiochila ludoviciana Sullivant var. invisa R. M. Schuster, Amer. Midl. Naturalist 63: 101. 1960, as “invisus”

Plants usually green, large, 3--4 mm wide. Branching largely terminal. Leaves imbricate, the strongly broadened postical bases shingled, +/- completely hiding stem in postical aspect, persistent, not fragmenting, narrow ovate-rectangular, usually more than 1.5 x as long as wide, postical leaf margin of sterile shoots not or obscurely undulate, postical leaf bases narrow, erect, forming a crista, leaves long-decurrent postically, vitta absent; margins subentire or entire, usually with 2--4 low, obtuse teeth at apex, postical margins entire or obsoletely 1--2-dentate; median cells averaging (17--)18--25(--28) \um wide, trigones often weak; apical cells large, (17--)18--40 x 22--40 \um wide; <cells of decurrent postical base almost equally thick-walled, only moderately elongated>. Oil bodies not seen. Underleaves of 2-several slender laciniae or lanceolate lobes. Propagula almost always with propagula. <Antical keel of perianth antical keel of perianth edentate>.

Oak tree, base of hardwood, Sapindus, cypress, limestone, mesic hammock, hardwoods forest; 0--50 m; Fla.

Plagiochila invisa is known only from several counties in Florida. It is similar to P. miradorensis and P. raddiana but differs in the postical leaf bases somewhat crisped and undulate but not forming water sacs, underleaves large laciniate-ciliate, and perianths without teeth on the antical keel, or rarely only one tooth.

13. Plagiochila micropteryx Gottsche, Ann. Sci. Nat., Bot. se´r. 5, 1: 107. 1864  C

Plagiochila diffusa Stephani

Plants usually green, large to very large, 3.5--5.5 mm wide. Branching largely terminal on mature plants. Leaves distant, spreading at 65--75 °, in drying tubular-involute; postical bases not densely shingled (leaving the stem conspicuously exposed in postical view), persistent, not fragmenting, lingulate-rectangular, 2--2.5(--3) x as long as wide, parallel-sided, the postical base neither dilated nor arched; <leaves distinctly bordered with 1--2 rows of elongate cells whose tangential walls are strongly thickened to form a border)>, short-decurrent, the decurrent strip flat or at most narrowly erect, vitta absent; marginal teeth of leaves few and low, largely on the rounded, truncate apex; median cells averaging (17--)18--25(--28) \um wide, collenchymatous (except in shade forms), always with thin walls and bulging trigones; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies of 1(--2) rows of coarse segments. Underleaves minute or obsolete, never of laciniae or lamellae. Propagula present, propagula only on postical leaf surface.

Sand, moist rocks, tree trunk, dry or wet forest; 0—50 m; Fla.; West Indies; South America (Brazil, Guyana, Peru).

Plagiochila micropteryx grows at rather high elevations in the Andes. [AW6] 

14. Plagiochila miradorensis Gottsche, Mexik. Leverm., 31. 1863   E

Plants usually green, large, 3--4(--4.5) mm wide. Branching largely terminal on mature plants. Leaves imbricate, the strongly broadened postical bases shingled, +/- completely hiding stem in postical aspect, leaves persistent, not fragmenting, ovate to rectangular-ovate, more than 1.5 x as long as wide, dilated postical leaf bases always +/- erect, postical leaf margin of sterile shoots not or obscurely undulate, postical leaf bases reflexed and convolute, forming a tubular water-sac of collenchymatous, scarcely elongated cells, usually bearing 2--6 spinose teeth, long-decurrent postically, vitta absent; margins of leaf apices entire to weakly dentate, <antical keel of perianth 2--4-dentate>; median cells averaging (17--)18--25(--28) \um wide, cell walls thin, trigones bulging, seldom confluent; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies botryoidal. Underleaves of 2--several linear, largely 1-seriate cilia. Propagula present.

Tree trunks, soil; 0—50 m; Ala., Fld., Ga., La., Miss., N.C., Tex.; Mexico.

Plagiochila miradorensis is similar to P. raddiana but the former differs in leaves less dentate and more falcate, the postical leaf base is spinose-dentate and convolute to form a water sac, cells of leaf apex nearly isodiametric, and underleaves smaller, of 2--4 filiform cilia.

1. Postical leaf base long-decurrent, reflexed-convolute and spinose-dentate or ciliate, antical leaf base moderatelly decurrent ... 14a. Plagiochila miradorensis var. miradorensis

1. Postical leaf bases short-decurrent, narrowly reflexed and reflexed margin usually entire, antical leaf base short-decurrent ... 14b. Plagiochila miradorensis var. convoluta

14a. Plagiochila miradorensis Gottsche var. miradorensis E

Postical leaf base long-decurrent, reflexed-convolute and spinose-dentate or ciliate, antical leaf base moderately decurrent.

Base of Magnolia and other hardwoods, exposed roots, Taxodium swamp, low hydric hammock, woody ravines, loess bluffs; 0—50 m; Ala., Fla., Ga., La., Miss., N.C., Tex.; Mexico.

Plagiochila miradorensis var. miradorensis is found in the outer coastal plain from North Carolina to Florida, west to Louisiana, Texas, and Mexico.

14b. Plagiochila miradorensis var. convoluta R. M. Schuster, Amer. Midl. Naturalist 63: 113. 1960 E

Postical leaf bases short-decurrent, narrowly reflexed and reflexed margin usually entire, antical leaf base short-decurrent.

Bark, base of swamp tupelo, semi-evergreen swamp forest; 85 m; Miss.

The var. convoluta is known only from the type from Jackson Co., Mississippi.

15. Plagiochila montagnei Nees Ann. Sci. Nat., Bot., se´r. 2, 5: 53. 1836

 Plagiochila hypnoides Willdenow ex Lindenberg

Plants usually green, very large, 4--5.5 mm wide. Branching largely terminal on mature plants. Leaves imbricate, the strongly broadened postical bases shingled, +/- completely hiding stem in postical aspect, persistent, not fragmenting, asymmetrically ovate to ovate-oblong, usually more than 1.5 x as long as wide, with dilated postical bases, entire postical leaf margin sharply spinose-dentate, including the somewhat cristate basal region, short-decurrent postically, vitta absent; margins with few (5--16) coarse teeth, these sometimes vestigial and never finely spinose, the larger broad-based, postical leaf margin sharply spinose-dentate, including the somewhat cristate basal region; median cells averaging (17--)18--25(--28) \um wide, cell walls strongly collenchymatous, trigones very large and bulging; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies botryoidal. Underleaves distinct to large. Propagula on postical surface of leaves.

Hardwood bark, base of Rapanea punctata, hammocks, cypress swamp; 0--100 m; Fla.; Mexico; West Indies; Central America; South America.

The laminal margins of Plagiochila montagnei have sharp and evenly spinose denticulations, postically short-decurrent with a ridge, not a water-sac, and underleaves are present.

16. Plagiochila ovalifolia Mitt., Trans. Linn. Soc. Lon- don, Bot. 3: 193. 1891

Plants usually dull green, large to very large, 2.5--6 mm wide. Branching normally all intercalary (from leaf axils). Leaves contiguous to remote, widely spreading, persistent, not fragmenting, short- to quadrate-ovate to suborbicular, usually (0.8--)1--1.4 x as long as wide, antical margin moderately to slightly reflexed at apex, often broadly truncate or trancate-2-lobed, short-decurrent antically and postically, vitta absent; margins mostly provided with a few irregular teeth; median cells 20--25 \um wide, cells thin-walled, trigones present, concave to somewhat bulging; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies opaque and granulose. Underleaves minute, filiform to 2--4-fid and ciliate. Propagula absent.

On boulder; 900 m; Oreg. (Curry Co.); e Asia.

Plagiochila ovalifolia is only weakly distinguished from P. porellioides by laminal margins dentate to denticulate, 2--3 layers of cortex versus 3--5, and perianth mouth commonly ciliate, not dentate.

SELECTED REFERENCE Bakalin, V. 2012. A small collection of hepatics from Oregon and California (western North America). Arctoa 21: 201--205.

17. Plagiochila patula (Swartz) Nees & Montagne ex Lindenberg, Sp. Hepat. (fasc. 1): 21. 1839

Jungermannia patula Swartz, Fl. Ind. Occid., 3. 1806; P. dubia Lindenberg & Gottsche; P. dubia Lindenberg & Gottsche var. integrifolia R. M. Schuster

Plants usually green, large, 3--4 mm wide. Branching largely terminal. Leaves widely spreading (65--70 deg,), approximate to laxly imbricate, postical bases not densely shingled (leaving the stem conspicuously exposed in postical view), persistent, not fragmenting, +/- ovate, subrectangular or narrowly ovate, widest near base, not distinctly bordered, not convolute in drying, 1.9--2.4 x as long as wide, the postical base somewhat broadened, postical leaf margins above broadened base almost at right angles to stem, short-decurrent, the decurrent strip flat or at most narrowly erect, vitta absent; marginal teeth small to weakly spinose; <perianth mouth with usually relatively low, inconspicuous teeth>; median cells averaging (17--)18--25(--28) \um wide, cell walls collenchymatous (except in shade forms), median cells with thin walls and bulging trigones; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies very coarsely segmented. Underleaves minute or obsolete, never of laciniae or lamellae. Propagula usually in part on adaxial (antical) leaf faces.

Bark at base of trees, trunk of Magnolia and Acer, soil, rock at bluff base, creek and ravine banks, floodplains, hydric hummock, Nyssa swamp; 1--100 m; Ala., Fld., Ga., La., Miss., N.C., S.C.; Mexico; West Indies; Central America; South America.

Plagiochila patula resembles P. raddiana to some extent, but differs in the broadly winged and dentate antical keel of the perianth.

18. Plagiochila porelloides (Torrey ex Nees) Lindenberg, Sp. Hepat. (Lindenberg) (fasc. 2--4): 61. 1840

Jungermannia porelloides Torrey ex Nees, Naturgesch. Eur. Leberm. 1: 170. 1833; Plagiochila satoi S. Hattori var. magna W. B. Schofield & W. S. Hong; P arctica Bryhn & Kaal. var. subarctica (Jørgensen) Inoue; P. asplenioides (Linnaeus) Dumortier subsp. porelloides (Torrey ex Nees) R. M. Schuster; P. asplenioides (Linnaeus) Dumortier var. obcampanulata R. M. Schuster; P. asplenioides (Linnaeus) Dumortier var. subarctica Jørgensen; P. porelloides (Torr. ex Nees) Lindenberg var. subarctica (Jørgensen) Lammes

Plants usually dull green, large to very large, 2--6 mm wide mm. Branching intercalary (from leaf axils). Leaves laterally spreading, occasionally postically secund, persistent, not fragmenting, nearly orbicular to broadly ovate-rounded, usually (0.8--)1--1.4 x as long as wide, antical margin broadly reflexed for nearly entire length, short-decurrent antically and postically, vitta absent; margins entire to dentate with (15--)20--35 short, fine teeth; median cells small, 18--32 \um wide, cell walls thin-walled, trigones present, concave to somewhat bulging; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies segmented. Underleaves minute, filiform to 2--4-fid and ciliate. Propagula absent.

Humus, clay, boulder, granite, sandstone, limestone, emergent rocks of spring, near creek, low montane forest, hardwood forest, mixed coniferous-deciduous woods; 200--2000 m; Greenland; Alta., B.C., Man., N.B., Nfld. & Labr. (Nfld.); Nun., Ont., P.E.I., Que.; Ala., Ark., Alaska, Ariz., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kan., Ky., Maine, Mass., Mich., Minn., Mo., Mont., N.H., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., S.Dak., Tenn., Vt., Wash., W.Va., Va., Wisc., Wyo.; Mexico; Eurasia.

R. M. Schuster (1980: 375) and N. A. Konstantinova & A. Potemkin (1996: 140) recognized Plagiochila porelloides var. subarctica at the level of form, a rank not recognized in FNA, and it is here placed in synonymy. Plagiochila columbiana is similar to P. porelloides but is readily distinguished by its small medial laminal cells, these 25l--33 /um versus 35--40 /um. The key suffices to distinguish the closely related P. asplenioides.

SELECTED REFERENCES Konstantinova, N. A. & A. Potemkin. 1996. Liverworts of the Russian Arctic: An annotated checklist and bibliography. Arctoa 6: 125--150.

19. Plagiochila punctata (Taylor) Taylor, London J. Bot. 5: 261. 1846

Jungermannia punctata Taylor, Trans. Bot. Soc. Edinburgh 1: 179. 1843

Plants green, small, 1--1.5 mm wide. Branching intercalary. Leaves remote to imbricate, erect to wide-spreading, caducous at base leaving sections of stem bare, obovate, 2--3 lobed, narrow near base, with postical margin not dilated basally, about 3 x as long as wide, lobes sharp or triangular, leaves short-decurrent antically, vitta weakly defined; margins usually dentate, when mature with 3--8(--15) sharp teeth; median cell width 18--32 \um, cell walls collenchymatous, trigones usually large and convex; apical cells 18--25 \um wide. Oil bodies coarsely segmented. Underleaves vestigial, of a few cells. Propagula propagula absent.

Base of sandstone cliff in rock-house area; elevation not given; Tenn.; South America; Europe; Africa.

Young or weak shoots of Plagiochila punctata are quite like those of P. exigua, but more mature shoots have leaves with up to 15 teeth.  The species is known from a single collection in our area, in the Cumberland Plateau of Tennessee, but the exact locality was not given by P. D. Davison et al. (2006)

SELECTED REFERENCE Davison, P. G., D. K. Smith, K. Feldberg, M. Lindner & J. Heinrich 2006 Plagiochila punctata (Plagiochilaceae) in Tennessee, new to North America Bryologist 109: 242–246

20. Plagiochila raddiana Lindenberg, Sp. Hepat. (Lindenberg) (fasc. 1): 9. 1839

Plagiochila ludoviciana Sullivant in A. Gray

Plants usually green, large to very large, 3--4(--5) mm wide. Branching largely terminal on mature plants. Leaves imbricate, the strongly broadened postical bases shingled, +/- completely hiding stem in postical aspect, persistent, not fragmenting, obliquely ovate, usually more than 1.5 x as long as wide, postical leaf margin of sterile shoots not or obscurely undulate, postical leaf base narrow, erect, forming a crista, leaves long-decurrent postically, vitta absent; margins +/- sharply spinose-dentate, usually with 2--3(--5) coarse apical teeth, postical leaf base edentate (rarely with 1--2 teeth); median cells averaging 18--25(--28) \um wide, cell walls with strongly bulging trigones; apical cells large, 18--40 x 20--40 \um wide, <cells of decurrent postical base elongated, narrow, usually strikingly thick-walled and +/- collenchymatous>. Oil bodies of a few coarse protuberant segments. Underleaves of 2-several slender laciniae or lanceolate lobes. Propagula usually present.

Vertical sandstone bluff, siliceous boulder, rock outcrop, bark, Celtis laevigata bark, base of Carpinus, beech, oak trunk, bank of river, oak woods and swamp; 10--700 m; Ala., Ark., Fla., Ga., La., Miss., N.C., Okla., S.C., Tenn., Tex., Va.; Mexico; West Indies; Central America; South America.

Plagiochila raddiana is a species with large size, narrow, ovate tapering leaves, propagula on the postical lamina, and large, bulging trigones. It is distinguished from the similar P. montagnei by its laciniate underleaves and long-decurrent, edentate postical leaf bases.

21. Plagiochila retrorsa Gottsche, Mexik. Leverm., 67. 1863

Plagiochila sharpii H. L. Blomquist

Plants usually +/- bronzed, with at least stem brownish, large, (1.5--)2--3 mm wide. Branching monopodial, rarely dichotomous. Leaves approximate to somewhat imbricate, spreading at about 45--70 °, persistent, not fragmenting, triangular-ovate to broadly ovate, cnemis strongly developed, postical margin strongly dilated and weakly arched, 1--1.4 x as long as wide, long-decurrent antically, short-decurrent postically, vitta with elongate (3--6:1) cell; marginal teeth fine, of 2--4(--5) cells in length; median cells +/- collenchymatous, 17--24 \um wide, trigones strong and bulging; apical cells 17--20 wide \um wide. Oil bodies homogeneous. Underleaves minute to small, grading from one slime papilla to several rows of 1-seriate cilia. Propagula absent.

Moist rocks, vertical sandstone, bluff, spruce-fir zone; 600--1000 m; Ga., Ill., N.C., S.C., Tenn.; Mexico; Central America; e Europe, Atlantic Islands.

Plagiochila retrorsa is similar to P. asplenioides but differs in a darker, olive green coloration, smaller laminal cells with large trigones, and presence of a vitta. The oil bodies of P. retrorsa are homogeneous but those of P. asplenioides are botryoidal.

22. Plagiochila sciophila Nees ex Lindenberg, Sp. Hepat. (Lindenberg) (fasc. 2–4): 100. 1840

Plagiochila acanthophylla Gottsche; P. acanthophylla Gottsche subsp. japonica (Sande Lac.) Inoue; P. acanthophylla Gottsche subsp. ciliigera (R. M. Schuster) R. M. Schuster; P. acanthophylla Gottsche var. ciliigera (R. M. Schuster) Inoue; P. japonica Sande Lac. subsp. ciliigera R. M. Schuster; P. euryphyllon Carl subsp. euryophyllon; P. sciophila subsp. ciligera (R. M. Schuster) L. Söderström

Plants usually shining green, very large, 3--4 mm wide. Branching intercalary (from leaf axils). Leaves patent, persistent, not fragmenting, narrow, oblong to rectangular, postical margin almost straight, the rounded or subtruncate leaf apices not or hardly 2-lobed, 1.5--2 x as long as wide, antical margin short-decurrent, postical base not or short-decurrent, vitta absent; margins with relatively few, 4--12(--15) elongate, spinose to finely spinose teeth each terminating in a row of (3--)4--6 strongly elongate cells; median cells averaging 25--40 \um wide, cell walls thin or weakly thickened, trigones small to moderately large, concave; apical cells large, (17--)18--40 x 22--40 \um wide. Oil bodies finely granular-segmented. Underleaves vestigial or of 1--2 cilia. Propagula absent.

Calcareous rock, shaded vertical limestone; 120--200 m; Ark.; e Asia.

Plagiochila sciophila is distinguished by a shining cuticle, intercalary branching, and the mostly uniseriate, elongate, ciliate marginal teeth. Only two North American collections are known, these from Stone Co., Arkansas, near Big Sink Hole and Blanchard Springs Caverns.

23. Plagiochila semidecurrens (Lehmann & Lindenberb) Lindenberg, Sp. Hepat. (fasc. 5): 142. 1843

Jungermannia semidecurrens Lehmann & Lindenberg in Lehmann, Nov. Stirp. Pug. 4: 21. 1832

Plants usually +/- bronzed, with at least stem brownish, plant large, 2.5--4 mm wide. Branching intercalary. Leaves slightly to closely imbricate, obliquely spreading, persistent, not fragmenting, ovate to ovate-triangular, postical margin strongly dilated and weakly arched, cnemis strongly developed, 1-1.5 x as long as wide, antical leaf base strongly decurrent, the postical moderately decurrent, vitta cells elongate, 3--6:1, mostly equally thick-walled, 13--16(--18) \um wide; marginal teeth coarse, 3--6(--10) cells in length; median cell width 15--20 x 15--20(--25) \um, trigones small to large, nodose; apical cells 14--17 \um wide. Oil bodies indistinctly granular. Underleaves vestigial, of a few cells. Propagula absent.

Western North America, e Asia.

1. Plants glossy, dark green, in cross section stem 20--28 cells thick, cortical cells in 3--4(--5) layers, seldom branched; leaves oblong to oblong-ovate, marginal teeth 15--30(--45), 1--4 cells in length ... 2a. Plagiochila semidicurrens var. semidecurrens

1. Plants dull, yellowish green, in cross section stem 11--15 cells thick, cortical cells in 2–3 layers, with sparse intercalary branching; leaves broadly ovate to suborbicular, marginal teeth 7--15, ca. 6 cells in length ... 23b. Plagiochila semidecurrens var. alaskana

23a. Plagiochila semidecurrens var. semidecurrens

Plagiochila sharpii H. L. Blomquist subsp. yakusimensis (S. Hattori) R. M. Schuster

Plants glossy, dark green, transection stem 20--28 cells across, cortical cells in 3--4(--5) layers, seldom branched; leaves oblong to oblong-ovate, marginal teeth 15--30(--45), 1--4 cells in length.

Cedar trunk, base of conifer, logs near lake short, damp cliff near waterfall, forest; 0--200 m; B.C.; e Asia.

Plagiochila semidecurrens var. semidecurrens is found in western North America; and in eastern Asia including the Himalayas.

23b. Plagiochila semidecurrens var. alaskana (A. Evans) Inoue, J. Hattori Bot. Lab. 28: 216. 1965

Plagiochila alaskana A. Evans, Bull. Torrey Bot. Club 41: 590. 1915, P. fryei Evans

Plants dull, yellowish green, transection stem 11--15 cells across, cortical cells in 2–3 layers, sparse intercalary branching; leaves broadly ovate to suborbicular, marginal teeth 7--15, ca. 6 cells in length.

Cliff, rocks, bark of trees; low to high elevations; B.C.; Alaska,, Oreg. .; e Asia (Japan).

Plagiochila semidecurrens var. alaskana is known from coastal Alaska including Adak Island in the Aleutians, and coastal British Columbia and Oregon.

SELECTED REFERENCE Majumdar, S. & T. Katagiri. 2020. Taxonomic status of Plagiochila semidecurrens var. alaskana and P. semidecurrens var. longifolia (Plagiochilaceae). Hattoria 11: 31–39.

24. Plagiochila sullivantii Gottsche ex A. Evans, Bot. Gaz. 21: 191. 1896 E

Plants deep green to brownish, large, 1.5--2.5 mm wide. Branching intercalary. Leaves distant to approximate, spreading at about 45 °, caducous at base, obovate, normally averaging less than 2 x as long as wide, not 2-lobed, narrow near base, with postical margin not dilated basally, 1.3--1.6 x as long as wide, leaves short-decurrent antically, vitta absent; margins with 3--9 or more sharp teeth, teeth narrow, usually spinose or finely spinose; median cell width 18--25 \um, cell walls thin to evenly thick-walled, trigones small and concave; apical cells 22--25 \um wide. Oil bodies botryoidal. Underleaves of (1--)2--4 short filaments. Propagula absent.

Rock; 350--1000 m; e U.S.A.

1. Leaves with usually 5--10 marginal teeth, [AW7]  3--4 cells in length ... 24a Plagiochila sullivantii var. sullivantii

1 Leaves commonly with 10--15 marginal teeth, 4--5(--7) cells in length... 24b. Plagiochila sullivantii var. spinigera

24a. Plagiochila sullivantii var. sullivantii E

Leaves with usually 5--10 marginal teeth, these up to 120 /um and 3--4 cells in length.

Soil on boulder, rock near stream, vertical shaded rocks, siliceous bluff, trunk of magnolia, mixed mesophytic forest, rich hardwood forest; 0--1000 m; Conn., Fld., Ga., Ky., Miss., N.Y., N.C., S.C., Tenn., Va., W.Va.

Plagiochila sullivantii var. sullivantii is endemic to the Appalachians south to Georgia and north to Vermont, and coastal areas of the southeastern states.

24b. Plagiochila sullivantii Gottche ex A. Evans var. spinigera R. M. Schuster, Amer. Midl. Naturalist 62: 323. 1959 C E

Leaves commonly with 10--15 marginal teeth, these [AW8] up to 180 /um and 4--5(--7) cells in length

Shaded wet rock, near waterfalls; 760--950 m; N.C. (Burke and Jackson cos.).

Plagiochila sullivantii var. spinigera is only known from two collections in North Carolina, at Whitewater Falls and Linville Gorge.

25. Plagiochila undata Sull. in Gray, Amer. J. Sci. Arts Ser. 2, 1: 73. 1846

Plants green, large, 2.5--3.5 mm wide. Branching largely terminal on mature plants. Leaves imbricate, the strongly broadened postical bases shingled and +/- completely hiding stem in postical aspect, persistent, not fragmenting, asymmetrically ovate-triangular to ovate, usually more than 1.5 x as long as wide, dilated postical leaf bases always +/- erect, postical leaf margin of sterile shoots strongly crispate-undulate, leaves long-decurrent postically, vitta absent; margins entire except for 1--several low teeth near apex; median cells averaging 17--25 \um wide, cell walls thin, trigones large, concave to bulging; apical cells large, 17--40 x 25--40 \um wide. Oil bodies botryoidal. Underleaves discrete to large. Propagula rare or absent.

Rock, chert, dolomite, limestone, sandstone, tree, hardwood forest, edge of spring, Nyssa-Taxodium swamp, hammock; 10--1409 m elevation; Ala., Ark., Fld., Ga., Ill., La., Mo., N.C., Ohio, S.C., Tenn.; Mexico; West Indies.

Plagiochila undata is distinctive in its large size, leaves nearly entire or weakly toothed apically, and undulate or crispate postical leaf margins, which are long-decurrent.

26. Plagiochila virginica A. Evans, Bull. West Virginia Agric. Exp Sta. 24: 497. 1892

Plants usually green; large, 2.5--3.5 mm wide. Branching terminal on mature plants. Leaves spreading at 55--75 ° from stem apex, approximate to laxly imbricate, postical bases not densely shingled (leaving the stem conspicuously exposed in postical view), persistent, not fragmenting, +/- ovate, postical base slightly to strongly dilated and arched, greatest width of flattened leaf near base, leaves not distinctly bordered, typically (1--)1.3--1.8 x as long as wide, postical base short-decurrent, the decurrent strip flat or at most narrowly erect, vitta absent; margins with 5--16 coarse teeth, these sometimes vestigial and acute, the larger broad-based; median cells averaging 17--28) \um wide; cell walls collenchymatous (except in shade forms), median cells with thin walls and bulging trigones; apical cells large, 17--40 x 20--40 \um wide. Oil bodies of 1(--2) rows of coarse segments, occasionally homogeneous. Underleaves minute or obsolete, never of laciniae or lamellae. Propagula present, confined to postical leaf surface.

Plagiochila virginica is distinguished by the shoots 2.5--3.5 mm wide, leaves ovate-rectangular to triangular and often long-decurrent, marginal teeth uneven, and postical leaf base not reflexed.

1. Leaves little or moderately imbricate, short-decurrent antically, margins with 4--10 short but distinct teeth... 26a. Plagiochila virginica var. virginica

1. Leaves closely imbricate, long-decurrent antically, margins with 3--5 weak denticulations .. 26b. Plagiochila virginica var. euryphylla

26a. Plagiochila virginica A. Evans var. virginica

Plagiochila virginica var. caroliniana R. M. Schuster, Amer. Midl. Naturalist 63: 15. 1960

Leaves little or moderately imbricate, short-decurrent antically, margins with 4--10 short but distinct teeth.

Vertical sandstone, limestone, clay, along streams, cliff; 150--1000 m; Conn., D.C., Ga., Ill., Ky., Miss., N.C., Ohio, S.C., Tenn., Va., W.Va.; Mexico.

The single known Mexico collection of Plagiochila virginica var. virginica was made by A. J. Sharp 2384c, TENN, det. H. Inoue, at 2600 m in Oaxaca from the base of an oak sapling.

26b. Plagiochila virginica A. Evans var. euryphylla R. M. Schuster, Amer. Midl. Naturalist 63: 21. 1960 C E

Leaves closely imbricate, long-decurrent antically, margins with 3--5 weak denticulations.

Moist rock; 1060 m; N.C. (Transylvania Co.).

Plagiochila virginica var. euryphylla is known only from the type from Transylvania Co., North Carolina.

EXCLUDED

Plagiochila porelloides (Torr. ex Nees) Lindenberg var. subarctica (Jørgensen) Lammes, Fl. Fenn. 6: 54. 1977; Plagiochila asplenioides (L.) Dumort. var. subarctica Jørgensen, Bergens Mus. Skr. 16: 173. 1934; Plagiochila arctica Bryhn & Kaal. var. subarctica (Jørgensen) Inoue

This Arctic taxon was recently recognized by N. A. Konstantinova and A. Potemkin (1996: 140) at the rank of forma, not recognized in FNA

SELECTED REFERENCE Konstantinova, N. A. and A. Potemkin. 1996. Liverworts of the Russian Arctic: An annotated checklist and bibliography. Arctoa 6: 125--150.

Plagiochila undata subsp. crispata (Gottsche) R. M. Schuster, Amer. Midl. Naturalist 63: 122. 1960. Basionym: Plagiochila crispata Gottsche, Mexik. Leverm.: 167. 1863.

Excluded by R.E. Stotler and B. Crandall-Stotler (2017).