BFNA Title: Porellaceae
Author:V. A. Bakalin 
Date: June 30, 2018
Edit Level: S
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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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XXX. PORELLACEAE  Cavers

Vadim A. Bakalin

Plants spreading from substrate or forming mats; branches replacing ventral half of a leaf; without flagella.  Leaves alternate, with dorsal lobe incubous, lobule succubous, lobe plane, with a small ventral lobe (lobule) folded under the large dorsal lobe, lobule attached to stem but not or only shortly attached to lobe, lobe entire, lobule often ciliate. Underleaves large, unlobed.  Rhizoids largely restricted to stem at base of underleaves. Specialized asexual reproduction lacking.  Gynoecium on a short lateral branch, without subfloral branches. Perianth well developed, dorsiventrally compressed, sometimes with 2--3 additional keels on ventral face, mouth broad or narrowed, perigynium absent.

Genera 2 (2 in the flora): North America, Mexico, Central America, South America, Eurasia, Africa, Pacific Islands, Australia.

Porellaceae are vigorous, definitely dorsi-ventrally compressed plants with bilobed leaves, dorsal lobe incubously inserted and far larger than ventral one. Among regional taxa Porellaceae may be mistaken for some large Lejeuneaceae from which Porellaceae differs even in sterile material by ventral lobe widely inserted across the stem (and commonly decurrent down the stem) and only shortly connected to the dorsal lobe. Porellaceae are distributed throughout the North America (although there are several states where no Porellaceae are recorded, but this is apparently the result of imperfect sampling). Species form rigid mats on various types of substrata, are commonly deep green, never pale or salad green, and rarely acquire blackish tints (except Ascidiota) or brown or even rusty pigmentation.

Porellaceae have well defined limits and there are no genera intermediate to other families. The genus Porella was recognized early by C. Linnaeus (when most of other leafy genera were treated as Jungermannia) and even earlier, by J. J. Dillenius.

1. Leaf margin entire to dentate, rarely ciliate, specialized water sacs absent, dorsal surface of the lobe smooth to weakly papillose, never with dome-like verrucae on each leaf cell … 1. Porella

1. Leaf margin more or less ciliate, ventral bases of lobes, lobules and the bases of underleaves with water-sacs, dorsal surface of leaf lobe coarsely verrucose, with one large dome-like papilla on each cell … 2. Ascidiota

XX. PORELLA Linnaeus, Sp. Pl. 2: 1106. 1753 * [Latin porellus, diminutive of porus, pore, the original reference to pores by J. Dillenius is unclear]

Vadim A. Bakalin

Madotheca Dumortier

Plants dorsiventrally compressed, more or less rigid, mostly deeply colored, varying from deep green to brownish and green-brown, rarely with rusty tint, no red pigmentation, creeping, rarely loosely ascending or with up-curved apices, forming loose mats not closely attached to the substratum. Stem 1--3-pinnately regularly or irregularly branched, rarely some of branches transformed into new main axes. Rhizoids rare, originating in area of contact between underleaf base and stem (both from the lowest cells of underleaf and from adjacent cells of ventral segment of the stem; commonly short, less than 1--1.5 mm in width, spreading obliquely down or upward from stem and forming brownish ‘rosettes’. Leaves divided into two unequal lobes, with dorsal lobe much larger than ventral lobule, united by very short to vestigial and virtually absent straight or arched keel, better developed in depauperate plants and in branches. Lobes incubously inserted, insertion line arcuate dorsally, contiguous to imbricate, convex to flattened, commonly with apex incurved towards ventral side of branch, rarely leaves flat, margins entire to crispate, angular and dentate, variously decurrent dorsally, when flattened on  the microscope slide obliquely ovate and obliquely triangular to rounded or widely lingulate, with apical portion rounded to attenuate to acute; cells in lobe middle thin-walled, mostly isodiametric to shortly oblong, with trigones of varying in size and shape, cuticle smooth. Lobules oblong to subrotund, most commonly ovate to triangular, plane to convex, with margins entire to dentate and ciliate, transversely to arcuately inserted, variously decurrent. Underleaves concave to convex, sinuously to transversely inserted, barely or up to two stem widths decurrent, lingulate to ovate, sometimes truncate, emarginated or clearly 2-lobed at the apex, margins plane to undulate, entire to crispate, angular, dentate and ciliate. Sexual condition dioicous. Androecia terminal, spicate, in specialized lateral branches (pinnae or pinnulae), rarely on non-specialized branch when ordinary branch becomes androecial one, with 5--15 or more pairs of bracts, monandrous; male bracts cup-shaped, 2-lobed for 1/3 of bract length by gamma-shaped sinus into two nearly equal lobes. Gynoecia terminal, on short lateral branches (sometimes appearing sessile), with or without normal leaves dividing female bracts from the main branch; female bracts keeled, with keel up 0.5 of longer lobe length, sheathing the perianth in proximal half and obliquely spreading distally; bracteole large, the same length as bracts or slightly shorter, obovate to lanceolate, sometimes divided into two lobes; perianth dorsiventrally compressed, not to distinctly plicate, slightly to strongly narrowed to the mouth, mouth entire to dentate and shortly ciliate along margin, exerted for 0.3--0.5 of its length. Seta short, 10--20 cells in diameter, slightly longer than perianth. Capsule spherical to shortly obovate, divided into 4--16 irregular valves. Spores pluricellular at maturity, large, verrucose. Elaters slender, 1--3-spiral. IKI reaction positive or negative.

Species ca. 100 (10 in the flora): North America, Mexico, Central America, South America, Eurasia, Africa, Pacific Islands, Australia.

The center of diversity of the genus Porella is Temperate to Subtropical Eastern Asia. Four of ten regionally recognized species (P. cordaeana, P. pinnata, P. platyphylloidea, P. platyphylla) are known from Europe, with the last also occurring in Asia. Three species are Western American temperate to south boreal endemics (P. bolanderii, P. navicularis, P. roellii). One species (P. swartziana) belongs to the group of Central American Subtropical to Tropical taxa and is known only from south-eastern extremity of the flora. Two species are also known in Temperate Eastern Asia, with one (P. fauriei) occurring in North America in isolated localities on Attu Island (Aleutians) and in Oregon. The second (P. japonica) is restricted in distribution to Appalachia and is represented in our area by the specialized ssp. appalachiana.

Infrageneric taxa of Porella are poorly understood. In addition to subg. Porella, subg. Protoporella R. M. Schuster is known for North America with one presumably East Asian species, P. fauriei. Within subg. Porella two sections were segregated. The first one (sect. Porella) includes six locally recognized taxa, with two described as western American endemics (P. roellii and P. navicularis) in subsect. Navicularis Hong. The second section (sect. Platyphyllae R.M. Schuster) includes three of 10 taxa present in North America. Due to high degree of intergradation of morphological features within the infrageneric taxa, these infrageneric taxa are not treated here.

One of valuable procedures in identification of Porella is IKI reaction testing. This helps separate some morphologically very closely related species. The method was described in the American literature by W. T. Doyle and R. E. Stotler (2006) and may be used as described as well as in the simplified manner given below. To test Porella specimens for IKI reaction put one small drop of common iodine alcohol solution (which may contain KI as well, which promotes solution of iodine in the alcohol) to a previously wetted branch on a microscope slide. If the reaction is positive, within a few seconds the cell content of the plant will get deep black or violet-black pigmentation. This method is universal for fresh and old material, at least some of tested specimens collected in the Nineteenth Century are still able to produce an intensive IKI reaction. Rarely this method may not work with some specimens collected in very wet (esp. submerged) habitats despite their age of collection.

For any identification procedures it is highly preferable to study leaves and underleaves from mature central stems, not branches. In the key and descriptions below, data on size and other morphological details is restricted to such structures. All measurements of length of lobes, lobules and underleaves were made from the middle of arched line of insertion to the end of the main axis of entity. The width measurements should be obtained in the widest area by the line perpendicular to length axis.

SELECTED REFERENCES  Doyle, W.T. & R.E. Stotler 2006. Contribution toward a Bryoflora of California III. Keys and Annotated species catalogue for Liverworts and Hornworts. Madrono 53(2): 89--197.  Hong, W.S. 1983. The genus Porella in North America West of the Hundredth Meridian. Bryologist 86(2): 143--155.  Piippo, S. & D.H. Norris 1996. A revision of Californian Porella (Hepaticae). Ann. Bot. Fenn. 33: 137--152.  Schuster, R.M. 1980. The Hepaticae and Anthocerotae of North America. Vol. 4. Columbia University Press, New York. Hentschel, J., Davison, P. G., and J. Heinrichs. 2008. Porella gracillima Mitt.(Jungermanniidae, Porellaceae) in Tennessee, with an Illustrated Key to the Porella Species of North America North of Mexico. Fieldiana Botany 47: 183--191.

1. IKI reaction positive.

2. Lobules narrower than stem, triangular, with acute apex, decurrent for 0.6--1.5 of stem width, commonly dentate in the decurrent area … 2. Porella cordaeana

2. Lobules wider than stem, ovate to rounded, mostly with rounded apex, rarely obtuse, not- or up to 0.5 of stem width decurrent.

3. Lobes subrotund, lobules similar in width to underleaves, elaters mostly 2-spiral (rarely 3-spiral) … 9. Porella platyphylloidea

3. Lobes oblong, lobules distinctly narrower than underleaves (mostly 0.6--0.75 of underleaf width), nearly obliquely ovate, elaters mostly unispiral (rarely 2-spiral in middle part of the elater) … 8. Porella platyphylla

1. IKI reaction negative.

4. Lobes dentate, at least near apex, rarely acute with 1--2 additional teeth only.

5. Underleaves, lobules and the most of the lobe  spinose-dentate throughout, lobes strongly incurved to ventral side of shoot, underleaves wider than long, not 2-lobed … 3. Porella fauriei

5. Underleaves, lobules and at least apical part of lobes sparsely to more or less densely toothed, lobes not- or slightly incurved the ventral side, underleaves longer than wide, commonly 2-lobed … 5. Porella japonica

4. Lobes smooth, rarely, as the exception, with short cilia or lacinae near dorsal lobe base.

6. Underleaves and lobules not decurrent, transversely or loosely arcuately or sinuously inserted, flattened or very loosely convex or concave, lobule sides nearly parallel.

7. Lobule length less than 0.5--0.6 of lobe width, lobule margins smooth to crispate and angular near base … 7. Porella pinnata

7. Lobule length more than 0.8 of lobe width, lobule margins spinose-ciliate near the base … 11. Porella swartziana

6. Leaves and underleaves deeply arcuately inserted, mostly decurrent, lobules convex to almost rolled, lobules triangle to ovate and suborbicular, so their sides are not parallel.

     8. Cells in lobe middle narrower than 20 \um wide, plants never brown … 4. Porella gracillima

     8.  Cells in lobe middle wider 20--25 \um, plants commonly brown in well-exposed sites.

     9. Cells in lobe middle with large, noticeable coarse, bulging trigones, underleaves and lobule widths nearly equal … 6. Porella navicularis

     9. Cells in lobe middle with small to moderate in size, mostly concave trigones, lobule narrower than underleaf (commonly 1.5--2 times narrower).

     10. Lobule decurrent for 0.5--1.5 of stem width below the keel level, commonly triangular, with more or less acute apex, nearly 1.5 as narrow as underleaf width … 1. Porella bolanderii

     10. Lobule not or hardly decurrent below keel level, ovoid, with rounded apex, nearly 1.8--2 times as narrow as underleaf width … 10. Porella roellii

1. Porella bolanderi (Austin) Pearson, List Canad. Hepat., 7. 1890   E

Madotheca bolanderi Austin, Bull. Torrey Bot, Club 3: 14. 1872

Plants deep green to brownish and brownish green, 3--4 mm wide and 7--15 cm long. Stem 2(--3) irregularly pinnately branched, some of branches transforming to main axis. Lobes contiguous to subimbricate, convex, rather imbricate, undulate at margin, sometimes crispate, commonly narrowly revolute to ventral side of stem and with apex recurved to ventral side of stem, dorsally shortly (up to 0.25 of stem width) decurrent, 1500--2900 x1600--2500 \um, obliquely ovate, with attenuate apex; cells in lobe middle nearly isodiametric, 20--37.5 x 20--32.5 \um, thin-walled, with moderate in size, triangular to slightly convex trigones, walls brownish. Keel wanting. Lobule convex, triangular to obliquely triangular, with recurved to ventral side margin, decurrent for 0.6--1.3 of stem width, apiculate, crenulate along margin, dentate in lower half, 400--1000 x100--500 \um. Underleaves trapezoidal to ovate, 1.3--2 of stem width, sinuously inserted, widely ovate, convex, undulate at margin, with margins recurved to ventral side, long decurrent (at one side longer than in another side), commonly 2-lobed at apex, in decurrencies crispate, angular to dentate. Perianth with a few (commonly with 2) main plicae ventrally, mouth ciliate. Spores 29--40 \um in diameter. Elaters 2-spiral, rarely 3-spiral. IKI reaction negative.

Shaded rocks and boulders, also bark of trees (mostly angiosperms) in broadleaved to coniferous forest zone; below 1500 m alt.; Calif., Oreg., Utah; endemic to Western North America.

Porella bolanderi may be mistaken for P. cordaeana and P. roellii. The best way to separate it from these is IKI reaction testing. Also, the lobules and underleaves are more contiguous in P. bolanderi and commonly overlap the one above. The species differs from P. roellii in long-decurrent ventral base of lobule (versus not or shortly decurrent) mostly acute lobule apices (versus not or obtuse). The latter feature is not universal and both acute and subrounded apices may be found in both species.

2. Porella cordaeana (Huebener) Moore, Rep. Irish Hepat., 2: 618. 1876

Jungermannia cordaeana Huebener, Hepaticol. Germ., 291. 1834; Porella rivularis (Nees) Trevisan

Plants deep green to yellowish green, not glossy, 2-pinnate, 2--3 mm wide and 7--10 cm long. Stem regularly 2-pinnately branched. Lobes contiguous, convex, with apex sometimes recurved to ventral side, dorsally decurrent for 0.25--1 of stem width, entire to loosely crispate, near dorsal base loosely dentate or angular; cells in lobe middle subisodiametric, 25--35 \um, thin-walled, trigones small to moderate in size, concave. Keel vestigial to virtually absent. Lobule triangular to lanceolate, arcuately inserted, decurrent for 0.6--1.25 of stem width, angular near ventral base and loosely to distinctly dentate along ventral side, canaliculate to rolled. Underleaves 1.2--1.9 of stem width, sinuously inserted, decurrent for 0.5--1.5 of stem width, undulate and shallowly crispate at the margin, sometimes dentate near base and in the decurrencies. Perianth broadly ovate, slightly gradually narrowed to the mouth, mouth virtually entire to dentate, commonly slightly curved to ventral side. Spores 30--40 \um. Elaters 200--250x8--10 \um, 2--3-spiral. IKI reaction positive.

Wet or rarely dry rocks, boulders, also shaded trees, rarely soil in humid place, in broadleaved to coniferous communities; mostly below 2000(--2750) m; Alta., B.C.; Alaska, Calif., Colo., Idaho, Mont., N.Mex., Nev., Oreg., Wash.; Europe.

Porella cardaeana may be mistaken for P. bolanderi, for differentiation see the latter. Also, there are problems in separating P. cordaeana from P. platyphylla. The former is characterized by very distant and acute lobules, these not wider than stem, versus contiguous or slightly distant and commonly rounded lobule apices in the latter species. The ventral side of lobule is commonly more coarsely toothed in P. cordaeana than in P. platyphylla, whose lobule margins commonly is entire to crispate and repand.

3. Porella fauriei (Stephani) S. Hattori, J. Jap. Botl. 20: 109. 1944

Madotheca fauriei Stephani, Sp. Hepat. 4: 315. 1910

Plants glossy, deep green, in loose patches, 1.3--1.8 mm wide and 5--10 cm long. Stem mostly irregularly 2-pinnately branched, some branches are transformed to main stem and start branching again. Lobes imbricate to (rarely) contiguous, convex, with apex strongly incurved to ventral side, obliquely ovate, densely dentate to ciliate-dentate at the apex and ventral side, and angular to crenulate in dorsal side, 100--1100 x750--800 mm; cells in the middle of lobe subisodiametric, 15--20 x 12.5--17.5 \um, thin-walled, with moderate in size to small, concave trigones. Keel ca. 0.2--0.25 of lobule length, rarely vestigial to absent. Lobules more or less flat, triangle to lingulate, arcuately inserted, not or up to 1/3 of stem width decurrent, densely dentate, with teeth longer toward base. Underleaves transversely elliptic, 2--2.5 stem width, dentate at the margin, shortly (up to 0.5 of stem width) decurrent, with teeth longer in the decurrencies. Perianth ovate, mouth nearly truncate, dentate to ciliate along margin. Spores unknown. Elaters unknown. IKI reaction negative.

More or less dry rocks and bases of shaded trees, in forestless areas to coniferous communities; tentatively below 200 m; Alaska, Oreg.; Eastern Asia.

Porella fauriei is a very distinct species due to its glossy appearance. It has the smallest cells among regionally recognized species, and densely ciliate-dentate margins of leaves and underleaves.

4. Porella gracillima Mitten, Trans. Linn. Soc. London, Bot. 3 (3): 202. 1891

Plants glossy, deep green or grayish green, apparently never brown, 1--2 mm wide and 5--20 cm long. Stem 2(--3) irregularly pinnately branched, some of branches transforming to main axis. Lobes commonly imbricate, rarely contiguous, convex, margin entire, with apex incurved to ventral side of stem, dorsally shortly (up to 0.25 of stem width) decurrent, 750--2200 x 600--950 \um, obliquely ovate, with rounded apex; cells in lobe middle nearly isodiametric, 10--22 x 8--20 \um, thin-walled to with walls slightly thickened, with moderate in size, concave, triangular to slightly convex trigones, walls brownish. Keel wanting. Lobule convex, sometimes loosely turbinate near the end, triangular with acute (but not prominently so) apex, decurrent for 0.5--1 of stem width, apiculate, margin in proximal third entire or obtusely dentate to roughly crispate-dentate and extending down as paraphyllose lines, 250--700 x180--300 \um. Underleaves ovate-triangular, 1--1.7 of stem width, sinuously inserted, apes ovate and sometimes reflexed, long-decurrent (at one side longer than in another side), commonly retuse at apex, in decurrencies entire to crispate, angular and dentate. Perianth with a few (commonly with 2) main plicae ventrally, mouth dentate. Spores unknown. Elaters unknown. IKI reaction negative.

Limestone outcrops in rich cove hardwood forest; ca. 500 m alt.; Tenn.; Asia.

Porella gracillima is malleable in ecology in East Asia where it is centrally distributed, growing in basic (including limestone) rocks and fine soils of basic (rarely neutral) reaction. The data on ecology in North America are limited to several collections from the same locality in Great Smoky Mountains National Park. Porella gracillima is a very distinctive by its glossy appearance and small leaf cells. It shares these features with P. fauriei, from which, however, it is readily differentiable in by entire lobe margins and long decurrent lobules and underleaves.

5. Porella japonica (Sande Lacoste) Mitten subsp. appalachiana R.M. Schuster , Hepat. Anthocerotae N. Amer. 4: 682. f. 639. 1980  E

Plants green to brownish green and bronzed, 1.6--2.5 mm wide and 3--7 cm long. Stem freely 1(--2)-pinnately branched. Lobes contiguous, slightly convex, oblong-obovate, angular to sinuously dentate or with 1--4-celled teeth; cells in the lobe middle subisodiametric, 21--24 \um in diameter, with moderate in size, convex trigones. Keel vestigial to virtually absent. Lobules, slightly convex, oblong to lingulate, irregularly coarsely spinose-dentate, often truncate-bidentate at apex, near to base with some cilia or spines. Underleaves  oblong, spinose-dentate, at base often ciliate or ciliate-dentate, 320--420 \um wide. Perianth unknown. Spores unknown. Elaters unknown. IKI reaction probably negative.

Shaded dry boulders or rocks in deciduous forest zone; 300--600 m alt.; N.C., S.C.

Porella japonica subsp. appalachiana is a subspecies endemic to Appalachia The report for China (Jia et al. 2016) is most probably mistaken. On the other hand, the status of this subspecies needs further study and may require species status. The typical subspecies is known from Temperate Eastern Asia.

SELECTED REFERENCE Jia, Y., Q. He, F. X. Li, S. He, M. Z. Wang and P. C. Wu. 2016. A newly updated and annotated checklist of the Anthocerotae and Hepaticae of Qinling Mts., China. Journal of Bryology, 38(4): 312--326.

6. Porella navicularis (Lehmann & Lindenberg) Pfeiffer, Fl. Niederhessen 2: 234. 1855

Jungermannia navicularis Lehmann & Lindenberg, Nov. Stirp. Pug. 6: 38. 1834

Plants yellowish brown, 2--3 mm wide and 8--20 cm long. Stem sparsely to frequently irregularly pinnately branched, rusty brownish to brownish. Lobes closely contiguous to more commonly subimbricate and imbricate, convex, with apex recurved to ventral side, shortly (up to 0.3 of stem width) decurrent dorsally, obliquely ovate, with rounded to loosely apiculate apex, 1200--2500 x 1000--1800 \um, margins revolute and sometimes undulate; cells in the lobe middle isodiametric, 17.5—25.0 \um, thin-walled, trigones large, sometimes confluent, bulging, cuticle smooth. Keel virtually absent. Lobules ovate, with apiculate apex, strongly convex, ca. 500--1000 x 350--750 \um when flattened on a microscope slide, long decurrent (ca. 0.6--1.3 of stem width). Underleaves trapezoidal to ovate, truncate at the apex, ca. 625--1000 x 700 \um, strongly convex, decurrent for 0.7--1.2 of stem width in both sides, decurrencies not dentate. Perianth obconic, with ventrally recurved apex and weakly dentate at mouth, not or loosely plicate, mouth spinosely dentate when young, teeth deciduous after sporangium exsertion. Spores 50--90 \um, bright yellowish green. Elaters 275--325 x 9--10 \um, 2(--3)-spiral. IKI reaction negative.

Rocks, logs and bark of angiosperm trees (most commonly on Quercus), more rarely on conifers in broadleaved to coniferous communities; mostly below 1000 m (highest point 2400 m); B.C.; Alaska, Calif., Idaho, Mont., Oreg., Wash., Wyo.; endemic to Western North America.

Porella navicularis is distinctive by the large, coarse, and noticeably bulging trigones that are not present in other locally recognized congeners. Depauperate phases may be mistaken for P. roellii, from which, aside of the trigone character, it is differs in perianth strongly curved near mouth towards the ventral side, such that it looks truncate, versus a flattened to weakly and unequally turned perianth in P. roellii. Also the perianth mouth is supposedly entire in P. navicularis (although spinose-dentate when nearly mature) and dentate to spinose-dentate in P. roellii, but this feature is not constant.

7. Porella pinnata Linnaeus, Sp. Pl. 2: 1106. 1753

Plants deep green to brownish green, 1.5--2.5 mm wide and 5--15 cm long. Stem freely branched, 2-pinnately branched, rarely mostly as archegonial dwarf branches, brownish. Lobes contiguous to more rarely distant, flattened to loosely convex-ridged, arcuately inserted, not or barely decurrent, contiguous, margins entire to very shallowly crispate or angular, obliquely lingulate, 1300--1875 x 950--1300 \um; cells in the middle of lobe subisodiametric to shortly oblong, 12.5--30 x 12.5--25 \um, thin-walled, trigones small to moderate in size, slightly convex to concave, sometimes with small intermediate thickenings. Keel vestigial to ca. 0.2 of lobule length, straight to slightly falcate. Lobule flat or very shallowly convex, oblong, rarely slightly falcate, with entire margins or shallowly angular, 450--550 x 175--325 \um, not or barely decurrent, angular near ventral base or smooth. Underleaves flat to concave, sinuously inserted, shortly (up to 0.25 of stem width) decurrent, ovate to lingulate, with truncate to more rarely emarginate apex, margins entire to shallowly crispate or angular, 450--625 x 375--500 \um. Perianth obovate to pyriform and elliptic, loosely plicate ventrally and smoothed dorsally, gradually narrowed to the narrow mouth, mouth dentate to shortly ciliate. Spores 30--42 \um in diameter. Elaters 170--240 x 9--14 \um, 2(--4)-spiral. IKI reaction negative.

Shaded stones and decaying wood in along the streams, including submerged stations, in these habitats as hygro- to hydrophyte. More rarely possesses mesophytic to even xerophytic nature and growing in bark of temperate trees and more or less dry decaying wood; lower elevation belts mostly below 500 m, the highest altitude found in Arkansas, where slightly mellow 1000 m; N.S., Ont., Que.; Ala., Ark., Fla., Ga., Ill., Ind., Iowa, Ky., La., Maine, Mass., Mich., Minn., Mo., N.C., N.H., N.J., N.Y., Ohio, Pa., R.I., S.C., Tenn., Tex., Va., Vt., W.Va., Wis.; Eurasia.

The species relatively rare in the westernmost Europe (report for China should be mistake for P. grandiloba), but is one of the commonest taxa of the genus in deciduous forest of eastern North America, especially Appalachian, slightly spreading to coniferous forest zone northward. Although the Flora of North America does not reflect taxonomy at the form level, R. M. Schuster (1980) strongly argued for recognition of infraspecific variation within the species. We agree and recognize three forms, one that is widely distributed both in North America and Europe, and two whose distributions are poorly understood. A key follows: 

1. Lobes convolute when dry, cells along lobe margins subequally or unequally thickened; south-east endemic … Porella pinnata fo. involuta (Hampe) R. M. Schuster

1. Lobes flattened to slightly incurved to ventral side, when dry, cells along lobe margins not thickened.

2. Lobule margins near ventral base entire; widely distributed in northern states … 6a. Porella pinnata fo. pinnata

2. Lobule margins near ventral leaf base with prominent tooth; probably Appalachian endemic … 6c. Porella pinnata fo. wataugensis (Sullivant) R. M. Schuster

8. Porella platyphylla (Linnaeus) Pfeiffer, Flora Niederhessen 2: 234. 1855

Jungermannia platyphylla Linnaeus, Sp. Pl., 1134. 1753

Plants green to brownish green or yellowish brown, 2.2--3 mm wide and 5--10 cm long. Stem freely regularly branched or nearly so, 2-pinnate, rarely 3-pinnate. Lobes contiguous to subimbricate, convex to nearly flattened, slightly incurved to ventral side, margins entire, with exception of dorsal base, where rarely angular, crispate to loosely denticulate,  barely decurrent dorsally, 1150--1350 x 950--1100 \um. Keel up 0.2 of lobule length or wanting. Lobules slightly convex, ovate, with rounded or obtuse apex, arcuately inserted, ca. 1.3--1.8 of stem width, ventrally decurrent for 0.25--0.5 of stem width, margins of decurrencies entire to undulate, crispate and slightly angular, 550--650 x 370--410 \um. Underleaves convex, widely ovate, 1.4--1.8 of stem width, undulate, with decurrencies denticulate, sometimes retuse at apex, with margins revolute towards the ventral side, 1.8--2 wider than lobules, 450--600 x 500--600 \um. Perianth ovate to obovate, slightly plicate (commonly with one ventral plica), inflated in distal half; mouth dentate to spinose-dentate and laciniate with branched teeth, flattened and commonly incurved to ventral side. Spores 36--55 x 36--40 \um. Elaters 200--275 x 7--10 \um, 2-spiral, and, locally partly 3-spiral. IKI reaction positive.

Shaded dry to wet rocks and bark of trees, in broadleaved to coniferous forests; below 2000 m; Alaska, B.C., Ont., Que.; Ariz., Colo., Conn., Fla., Ga., Idaho, Ill., Ind., Iowa, Ky., Maine, Mass., Mich., Minn., Mont., N.C., N.H., N.Mex., N.Y., Nebr., Ohio, Oreg., Pa., S.Dak., Va., Vt., W.Va., Wash., Wis., Wyo.; Eurasia.

Porella platyphylla may be easily confused with P. cordaeana and P. platyphylloidea, see both for distinctions.

9. Porella platyphylloidea (Schweinitz) Lindberg, Helsingfors Dagblad1876 (346)): 2. 1876.

Jungermannia platyphylloidea Schweinitz, Spec. Fl. Amer. Crypt., 9. 1821; Porella platyphylla var. platyphylloidea (Schweinitz) Frye & L. Clark

Plants green to brownish green or yellowish brown, 2.2--3 mm wide and 5--10 cm long. Stem freely regularly branched or nearly so, 2-pinnate.  Lobes contiguous to subimbricate, mostly convex, slightly incurved to ventral side, margins entire, with exception of dorsal base, where angular, crispate to loosely denticulate, barely decurrent dorsally, 1250--1800 x 1300--2000 \um. Keel vestigial to virtually absent. Lobules slightly convex, ovate, with rounded or obtuse apex, arcuately inserted, ca. 1.3--1.9 of stem width, ventrally decurrent for 0.25--0.5 of stem width, in decurrent area margins entire to undulate, crispate and slightly angular, 850--1050 x 700--800 \um. Underleaves convex, widely ovate, 1.4--1.8 of stem width, undulate, decurrencies denticulate, sometimes retuse at apex, with margins revolute to ventral side, 510--650 x 575--850 \um. Perianth ovate to obovate, slightly plicate (commonly with one ventral plica), inflated in distal half; mouth dentate to spinose-dentate and laciniate with branched teeth, mouth flattened, whereas apical part of the perianth is commonly curved to ventral side. Spores 40--45 x 34--37 \um. Elaters 1-spiral, rarely 2-spiral near middle. IKI reaction positive.

Humid to more or less dry bark and rocks in shaded to open places, in deciduous forest zone, slightly spreading to south coniferous zone, absent in subtropical and prairie communities; below 2000 m; Ont., Que.; Ariz., Ark., B.C., D.C., Fla., Idaho, Ind., Iowa, Ky., La., Maine, Mass., Md., ,Minn., Mo., Mont., N.C., N.H., N.Mex., N.S., N.Y., Ohio, Oreg., Pa., S.C., Tenn., Va., Vt., W.Va., Wash., Wis.; Europe.

Porella platyphylloidea may be easily confused with P. platyphylla. The intergrading morphology of gametophytes has resulted in many mistakes in identifications and in treating the taxon as simple synonym of P. platyphylla or as a variety of that species. Apparently the best distinction between the two species is elater characters, mostly 1-spiral in P. platyphylloidea and 2-spiral in P. platyphylla. Plants without sporophytes may be separated by longer than wide lobe in P. platyphylla, versus subrotund lobe in P. platyphylloidea; also, by lobules much narrower than underleaves in the former and almost equal in width in the latter. R. M. Schuster (1980: 669) also noted the difference in perianth mouth that is “with remote to moderately close, short, usually unbranched cilia” in P. platyphylla, versus “with crowded, often branched and clustered cilia” in P. platyphylloidea. The distinguishing features discussed above are not constant.

10. Porella roellii Stephani, Bot. Centralbl. 45(7): 203. 1891   E

Plants yellowish brown, 1.9--3 mm wide, 4--10 cm long. Stem regularly 2-pinnately branched, yellowish brown. Lobes contiguous to subimbricate, slightly convex to flattened, with apex recurved to ventral side, commonly shallowly crispate along margin, arcuately inserted, auriculate near dorsal base, where sometimes loosely angular, obliquely widely ovate to obliquely widely triangular, barely decurrent dorsally, 850--1700 x 650--1800 \um; cells in middle of the lobe subisodiametric, 17.5--30.0 x 17.5--27.5 \um, thin-walled, with trigones sharply defined (not smoothly intergrading with the walls), moderate in size, concave to slightly convex, walls thin. Keel virtually absent or very short. Lobules flattened to convex, ovate-triangular, attenuate, apex suddenly rounded, angular to denticulate near both bases, barely decurrent, sometimes shallowly crispate, commonly with ventral margins loosely recurved ventrally, rarely both margins (but not lobule apex) recurved, 925--1000 x 800--925 \um. Underleaves convex, widely ovate to trapezoidal, apex truncate to emarginate, margins recurved towards ventral side, loosely crispate to angular near base, 500--875 x 500--1150 \um. Perianth broadly obovate, not or loosely plicate, mouth flat (not curved), densely dentate to shortly laciniate, and then with additional lateral teeth on the margins of lacinae. Spores 32--38 \um. Elaters 150--250 x 7--10 \um, 2-spiral. IKI reaction negative

Dry shaded to open rocks, tree bark (mostly angiosperms), rarer on logs and soil, prefer humid habitats near streams in canyon, etc., in broadleaved to coniferous communities; below 1200(--1800) m; B.C.; Alaska, Calif., Idaho, Mont., Nev., Oreg., Wash.; endemic to western North America.

Porella roellii has the aspect of weakly developed P. navicularis, with which it may be easily mistaken; for distinctions see the latter. W. S. Hong (1983) segregated two forms of the species in addition to fo. roellii. However, taking into account morphological malleability of the species, we regard these “forms” as only phases of the species.

11. Porella swartziana (F. Weber) Trevisan, Mem. Reale Ist. Lombardo Sci., Ser. 3, Cl. Sci. Mat. 4: 407. 1877

Jungermannia swartziana F. Weber, Hist, Musc, Hepat. Prodr., 18. 1815

Plants yellowish brown to brown, 2.2--3 mm wide and 5--10 cm long. Stem brownish, freely 1(--2)-pinnately branched. Lobes contiguous, nearly plane, with ventral margins recurved to dorsal side such that leaves look slightly convex to obcanaliculate, not or barely decurrent, shallowly crispate along margin, sometimes ciliate near ventral or dorsal or both bases, mostly obliquely ovate, 1450--1550 x 1200--1300 \um; cells in the lobe middle isodiametric to slightly oblong, 22.5--37.5 x 22.5--30 \um, thin-walled, trigones moderate in size, concave. Keel vestigial, less than 1/5 of lobule length. Lobules plane to very shallowly convex to obcanaliculate, oblong-lingulate, sometimes slightly falcate, ciliate near ventral and lateral base, and entire at other segments of margin, 800--900 x 225--250 \um. Underleaves lingulate to narrowly trapezoidal, transversely to sinuously inserted, shortly (0.2--0.3 of stem width) decurrent, entire, but frequently dentate-ciliate near both bases, with rounded to emarginated apex, 750--825 x 450--550 \um. Perianth oblong-fusiform, obtusely triangular in cross section, mouth narrowed, almost beaked, lobulate and ciliate-dentate with teeth 2--3 cells long. Spores 24--35 \um. Elaters 2-spiral, 7--13 \um wide. IKI reaction negative.

Bark and dry rocks in subtropical forests; altitude unknown, below 500 m alt.; La.; Central America. 

Porella swartziana is a distinctive and easily recognized species due to its oblong-lingulate lobules with parallel or semi-parallel lateral sides. It may be mistaken for P. pinnata, from which it differs in longer lobules (ca. 0.9--1 of lobe width, versus 0.5--0.6 in P. pinnata), and spinose-ciliate dentation near ventral base of lobule (commonly with prominent horn-like tooth), versus margins entire to crenulate in P. pinnata. Porella swartziana has also been reported for Africa (Hentschel et al. 2007).

SELECTED REFERENCE Hentschel, J., R. L. Zhu, D. G. Long, P. G. Davison, H. Schneider, S. R. Gradstein, and J. Heinrichs. 2007. A phylogeny of Porella (Porellaceae, Jungermanniopsida) based on nuclear and chloroplast DNA sequences. Molecular Phylogenetics and Evolution 45: 693--705.

XX. ASCIDIOTA C. Massal. Nuovo Giornale Botanico Italiano, n.s. 5: 256. 1898 *

[Greek ascidion, sac, and otion, ears, alluding to sac-like auricles near lobe, lobule and underleaf bases]

Vadim A. Bakalin

Plants loosely dorsiventrally compressed, more or less rigid, deeply colored, varying from deep green to blackish brown and black, no red pigmentation, creeping to ascending commonly with down-curved apices, forming loose mats or among mosses, not closely attached to the substratum. Stem 1--2(--3)-pinnately regularly or irregularly branched. Rhizoids rare, originating in area of contact between underleaf base and stem; commonly short, less than 1--1.5 mm in width, spreading obliquely down or upward from stem and forming brownish ‘rosettes’. Leaves divided into two unequal lobes, with dorsal lobe much larger than ventral, called lobule, united by very short to vestigial and virtually absent straight or arched keel, better developed in depauperate plants and in branches. Lobes incubously inserted, insertion line arcuate dorsally, convex to plane, with apex incurved towards ventral side of branch, margins ciliate, variously decurrent dorsally, when flattened on the microscope slide obliquely ovate; cells in lobe middle thin-walled, mostly isodiametric to shortly oblong, with trigones large and sometimes confluent, cuticle smooth to weakly verrucose in midleaf and conspicuously verrucose along margin. Lobules ovate, plane to convex, with margins dentate and ciliate, transversely to arcuately inserted, barely decurrent. Underleaves concave, transversely inserted, not decurrent, lingulate to transversely elliptic, with water sacs near base. Sexual condition dioicous. Androecia unknown. Gynoecia terminal, on short lateral branches, female bracts and bracteoles nearly similar to leaves and underleaves, in 1–2 pairs. Otherwise unknown.   IKI reaction negative.

Species ca. 1 (1 in the flora): North America, Asia.

Selected references

Potemkin A.D., Y.S. Mamontov, E.A. Borovichev, V.E. Fedosov and E.V. Sofronova 2015. The genus Ascidiota C.Massal. (Porellaceae, Marchantiophyta) in North Asia. J. Bryol. 37: 49--55. Schuster, R.M. and W.C. Steere 1960. The hepatic genus Ascidiota Massalongo new to North America. Bull. Torrey Bot. Club 87: 209--215.

Steere, W.C. and Inoue, H. 1978. Hepaticae of Arctic Alaska. J. Hattori Bot. Lab. 44: 251--345.

1 Ascidiota blepharophylla C. Massalongo, Nuovo Giorn. Bot. Ital., n.s. 5(2): 257, pl.2. 1898

Ascidiota blepharophylla subsp. alaskana Steere & R.M. Schuster

Plants 1--1.4 mm wide and 15--30 mm long. Stem commonly with some branches transforming into new main axis. Rhizoids fasciculate. Leaves with short keel tending to transform into auriculate sac. Lobes contiguous to imbricate, arcuately inserted, sometimes with discolored margin, densely dentate-ciliate, with antical margin however commonly free of cilia and only crenulate, cilia become larger to the lobe bases, teeth or cilia 1--6 cells long, auriculate near dorsal base, in well-developed lobes with distinct sac near ventral base at joining with lobule, 750--1125 x 1125--1250 \um; cells in the lobe middle 20--25 \um in diameter, thin-walled, walls brownish, trigones large, sometimes confluent, convex, cuticle smooth to weakly verrucose; cells near dorsal base thin-walled, similar in size to those in lobe middle, but with more coarse trigones, external wall along lobe margin noticeable thickened, cells with large semi-spherical verrucae one for each cell lumen. Lobules plane to slightly convex, oriented perpendicularly to the lobe, dentate-ciliate throughout along margin, with free sac near ventral lobe, 300--550 x 150--200 \um, arcuately inserted, sometimes shortly decurrent. Underleaves slightly concave, loosely sinuately to transversely inserted, lingulate to transversely elliptic and ob-trapezoidal, with sacs near each lateral margin base, dentate-ciliate throughout, but more densely in lateral sides, 1--6 celled, up to 150--160 \um long, 550--775 x 650--875 \um; underleaf cuticle similar to those in lobe margin, with large verrucae above each cell. Dioicous? Gynoecia with 2--3 archegonia, terminal on lateral branches. Bracts and bracteole nearly similar to leaves. Antheridia unknown. Sporophytes unknown.

Among mosses and over moss patches, sometimes over bare ground in the places rich in Calcium in tundra zone, also cliffs in spruce and birch open woods; 150--700 m.; Alaska; Asia (China).

Ascidiota blepharophylla is known from a few collections from Chinese Shensi, Russian Siberia and a few localities in Arctic Alaska. In the work of W.C. Steere and R. M. Schuster (1960) the Alaskan populations of the species were regarded as separate subspecies (ssp. alaskana), however, after collecting additional and more copious material, Steere and Inoue (1978) concluded that wide intergrading and unstable differentiating features do not permit recognition of two subspecies. The species has very distinctive appearance and may be easily identified in the field by virtually black color, incubously oriented lobes, and ciliate leaf margins. The only reproductive structures currently known are the poorly represented gynoecia in type specimens).