BFNA Title:Aneuraceae
Author: J. Faubert
Date: March 29, 2015
Edit Level: R
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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ANEURACEAE  H. Klinggräff       

 

Jean Faubert

 

Plants thallose, terrestrial [aquatic], green to yellowish green, in one species creamy white [pallid green] and heterotrophic. Thallus lacking a strongly differentiated midrib, gradually thinning towards margins or with rounded margins; central strand absent; vegetative branching monopodial; rhizoids usually scattered over ventral surface of thallus, sometimes a few on the dorsal and lateral sides; slime papillae sessile, 1-celled, scattered, ephemeral; oil-bodies present or absent. Asexual reproduction frequent, by 1--2(--3)-celled endogenous gemmae, or absent. Sexual condition dioicous or monoicous, heterothallic or homothallic; antheridia in two rows, sunken in chambers on abbreviated lateral branches [on the main thallus]; archegonia with paraphyses in clusters, on abbreviated lateral branches [or on the main thallus]; sporophytes each enclosed by a clavate, multistratose, fleshy shoot calyptra surrounded by hairs, pseudoperianth absent; capsules ellipsoid to subcylindric, dehiscing by four valves, each one with an apical elaterophore, walls 2-stratose, outer wall cells with nodular thickenings. Spores 10--30 µm, long-coherent in tetrads or soon free, verruculose or alveolate; elaters 8--16 µm, generally 1-spiral.

 

Genera 4 (2 in the flora): worldwide, with highest diversity in Australasia.

 

1.   Thallus simple or irregularly pinnate (to coralloid in one species), segments 2--8(--10) mm wide, branches short and irregular; oil-bodies 2--4(--6) µm, colorless, 5--55 per cell  ................... 1. Aneura

1.   Thallus 1--3-pinnate, segments 0.2--2 mm wide, branches generally elongate; oil-bodies 6--18 µm, at least those of the hypodermal cells opaque, 1--10(--15) per cell, or absent in most cells of some species           2. Riccardia

 

1. ANEURA Dumortier, Comment. Bot. 115. 1822 * [ Greek a-, without, and neuron, sinew, tendon or cord, alluding to the absence of midrib]

 

Plants green to yellowish green or creamy white, apices of branches appressed to substrate. Thallus robust, 2--8(--12) mm wide, fleshy and brittle or herbaceous and translucent, lingulate to sublinear, simple or irregularly pinnate to coralloid; cross-section 10--20 cells thick medially; epidermal cells with 5--55 oil-bodies, these 2--4(--6) µm wide, ovoid to spheric to ellipsoid, colorless, male branches lateral, solitary or in clusters of 2--3; female branches short, lateral. Specialized asexual reproduction absent [present].  Sexual condition dioicous, heterothallic; males plants smaller and thinner than female plants, sometimes dwarfed; male branches solitary or in groups of 2--3 or sometimes more, female branches short, located in a lateral notch of the thallus, protected by proliferations from the thallus and its incurved margins; shoot calyptra clavate, thick and fleshy, smooth, tuberculate or hairy; capsule oblong-ovoid or subcylindric; wall inner cells with numerous annular or semiannular bands. Spores 15--30 µm, long-coherent in tetrads or not, verruculose or alveolate.

 

Species 7--8 (3 in the flora): worldwide except Antarctica.

 

1. Thallus creamy white, lacking chloroplasts; plants growing under mats of mosses, usually Sphagnum, with only the sporophytes emerging 2. Aneura mirabilis

1. Thallus green, chloroplasts numerous; plants growing on various substrates but not specifically under mats of mosses

2. Thallus thin, herbaceous, multistratose in the central part, 1-stratose at margins, the thallus thus presenting a prominent, thick costal region bordered by strongly undulate wings 2--32 cells wide 1. Aneura maxima

2. Thallus turgid, opaque, multistratose throughout, costal region not prominent, margins flat to slightly undulate (narrow wings may be present in specimens from very damp habitats) 3. Aneura pinguis

 

1. Aneura maxima (Schiffner) Stephani, Sp. Hepat. 1: 270. 1899

 

Aneura sharpii Inoue & N.G. Miller

 

Plants green, herbaceous, translucent. Thallus 5--7 cm x 5--8 mm, simple, lingulate or sparsely branched, showing a sharp boundary between costal region 6--12 cells thick and marginal wings 1 cell thick; margins undulate to crispate, (2--)6--32 cells wide, wider at distal end of thallus, narrowing proximally, the thallus thus appearing somewhat stipitate; lateral branches short and stipitate. Epidermal cells with 20--45 oil-bodies per cell, oil-bodies fewer or lacking in hypodermal cells. Rhizoids scattered on ventral side of costal region. Male plants somewhat narrower than female plants, sometimes appearing pinnulate from numerous androecial branches, these single or in groups of 2--3, each with 2--4 pairs of antheridia; female branches located in a lateral notch of the thallus, protected by proliferations from the thallus and its incurved margins. Capsule oblong-ovoid, 2.5 mm. Spores 21--26 µm, yellowish-brown, finely verruculose; elaters 1-spiral.

 

Shaded damp litter, alluvial deposits or rocks, most often along rivulets, brooks, seepage, pools or waterfalls; low elevations; N.B., Ont., Que., Conn., Ky., La., Maine, Mass., Miss., Mo., N.Y., N.C., Pa., Tenn., Vt., W.Va., Europe; Asia (including Indonesia); Pacific Islands.

 

In some colonies of Aneura maxima, sexual branches are very abundant, male plants may appear pinnulate, and female plants may produce sexual branches in most undulations of the margins. The presence of fertile organs on a specimen of Aneura will eliminate any doubt as to the genus at hand, but vegetative specimens need a closer study. Unbranched thalli of Aneura maxima have an overall aspect reminiscent of Pallavicinia or of some forms of Moerckia. In the absence of sexual organs, these two genera can be distinguished from Aneura by the presence in them of stalked slime papillae and of a central strand. Vegetative plants of Aneura maxima could also be mistaken for Pellia. Aneura maxima has slime papillae that are sessile and 1-celled, without associated hairs, and the rhizoids are thin and colorless.

 

SELECTED REFERENCE:

Frahm, J.-P., 2012. Cultivation experiments with Aneura pinguis. A contribution to the separation of Aneura maxima and A. pinguis. Arch. Bryol. 136: 1--6.

 

2. Aneura mirabilis (Malmborg) Wickett & Goffinet, Bot. J. Linn. Soc. 156: 11. 2008

Cryptothallus mirabilis Malmborg, Ann. Bryol. 6: 122. 1933

 

Plants fleshy, creamy white. Thallus 2--4 cm x 2--5 mm, simple to abundantly pinnate, or coralloid, ventral portion strongly mycorrhizal with age; margins rounded, sinuous, tumid, often ascending. Cells lacking chloroplasts, epidermal cells lacking oil-bodies or with 6--12 oil-bodies, hypodermal cells with 40--50 oil-bodies. Rhizoids scattered on ventral and lateral sides of thallus, with a few on dorsal side. Male plants dwarfed, each androecial branch with 2--8 antheridia in two ranks; female branches short with gynoecium produced at apex, surrounded by capillary, uniseriate and contorted hairs. Capsule sub-cylindric, 2--3 mm long, dehiscing below or above the mat of mosses overlaying the thallus. Spores 24--30 µm, dark-brown, alveolate, with 4--6 alveolae across the surface; elaters 1-spiral.

 

Growing under mats of mosses, usually, but not restricted to, Sphagnum [under leaf litter], with only the sporophytes emerging above the surface; low elevations; w Greenland; Europe.

 

Aneura mirabilis is the only non-photosynthetic bryophyte. Furthermore, it is the only land plant with a dominant non-photosynthetic haploid generation. The plant is heterotrophic, acquiring carbon by taking advantage of an existing mycorrhizal association between an ectomycorrhizal basidiomycete, Tulasnella, and a host tree (usually Pinus or Betula). The basidiomycete becomes endophytic, forming intracellular coils in the thallus of the liverwort. Aneura mirabilis is thus considered parasitic on the fungal endophyte, and is not strictly a saprophyte. The single Greenland collection is without sex organs.

 

SELECTED REFERENCE:

Bidartondo M. I., T. D. Bruns, M. Weiss, C. Sérgio and D.J. Read. 2003. Specialized cheating of the ectomycorrhizal symbiosis by an epiparasitic liverwort. Proc. Roy. Soc. London, Ser. B: Biol. Sci. 270: 835--842.

Wickett N. J. and B. Goffinet. 2008. Origin and relationships of the myco-heterotrophic liverwort Cryptothallus mirabilis Malmb. (Metzgeriales, Marchantiophyta). Bot. J. Linnean Soc. 156: 1--12.

 

3. Aneura pinguis (Linnaeus) Dumortier, Comment. Bot. 115. 1822

Jungermannia pinguis Linnaeus, Sp. Pl. 1136. 1753; Aneura pinguis var. angustior (Hooker) R.M. Schuster

 

Plants green, nearly opaque, appearing greasy. Thallus 2--3(--5) cm x 2--6 mm, simple, fleshy and brittle, lingulate to sublinear or occasionally sparsely branched, 10--20 cells thick medially, becoming gradually thinner toward the margins; margins appearing swollen, obscurely crisped or undulate, sometimes flat, 1--3 cells thick; branches irregular, sparse. Epidermal cells with 6--20 oil-bodies. Rhizoids numerous on ventral side. Male plants smaller and thinner than female plants; male branches in groups of 2--3, each with 3--5 pairs of antheridia; female branches located in a deep sinus of the thallus, protected by proliferations from the thallus and its incurved margins. Capsule oblong-ellipsoidal, (1.5--)2--2.5 mm. Spores 15--24 µm, reddish-brown, alveolate, finely verruculose; elaters generally 1-spiral, occasionally 2-spiral.

 

Mineral soil, wet peaty soil, bogs and fens, seepage areas on rock faces, alluvial deposits, damp litter, rotting logs, pile of mine slag devoid of any other life-form; low to high elevations; Greenland; Alta., B.C., Man., N.B., Nfld. and Labrador, N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine,Mass., Mich., Minn., Miss., Mo., Mont.,  Nev., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., S.C., Tenn., Vt., Va., Wash., W.Va., Wis., West Indies; Central America; South America; Arctic; Eurasia, Asia (including Indonesia); Africa (including Madagascar); Atlantic Islands; Australia.

 

Aneura pinguis is a calcium-tolerant species forming patches or sometimes occurring as single plants creeping among other bryophytes. It is to be found in a vast array of habitats. The wide ecological amplitude is correlated with a cosmopolitan distribution. It is also an indication that the species could actually represent a complex of several cryptospecies, which would be difficult to segregate because of the morphological simplicity of the plants.

 

 

2. RICCARDIA Gray, Nat. Arr. Brit. Pl. 1: 679. 1821 * [For members of the Italian family Riccardi, mentioned as having supported Micheli's Nova Plantarum Genera]

 

Plants pale to dark green, sometimes brownish in older parts, prostrate, apices of branches somewhat ascending and tufted when crowded. Thallus delicate, regularly or irregularly 1--3-pinnate or palmately branched, 0.2--2 mm wide, branches 0.15--2 mm wide, lingulate or linear; cross-section 3--9 cells thick medially; epidermal cells with 1--10(--15) oil-bodies, these 6--36 µm wide, ovoid to spheric, ellipsoid or fusiform, opaque, brownish or grayish, sometimes inconspicuous, absent in one species. Specialized asexual reproduction frequent or rare, by 1--2(--3)-celled endogenous gemmae produced in epidermal cells of thallus apices. Sexual condition dioicous or monoicous, homothallic when dioicous; male branches linear to short-lingulate, surrounded by proliferations from the epidermal cells; female branches very short, protected by the incurved margins of the thallus or by proliferations from the epidermal cells, never located in a lateral notch of the thallus; shoot calyptra multistratose, smooth or verruculose above; capsule ellipsoidal; wall inner cells lacking thickenings or semiannular bands. Spores 10--17 µm, not long-coherent, verruculose.

 

Species: 90--100 (6 in the flora): worldwide except Antarctica.

 

The oil-bodies and the sexual condition must be carefully examined in order to obtain a confident identification of any Riccardia specimen. The identification of dry and sterile material is very difficult, or may be impossible, as secondary characters are notoriously variable and overlapping, especially if all the taxa occurring in the flora area are potential candidates. On the other hand, once familiar with a reduced number of regional taxa, one can easily recognize those, even in the field.  Oil-body presence and number must be observed in both the epidermal and hypodermal cells, and their distribution in the marginal and central parts of the thallus should be noted. Careful and patient manipulations are required to isolate individual thalli from the tangle of each colony and attached substrate, in order to establish the presence and organisation of fertile branches. Care is required, since colonies often comprise more than one species. Although fertile plants appear to be common (at least in the north-eastern part of North America), mature capsules are seldom observed. Thus capsule characters are not used in the following key.

 

 

1. Dioicous 5. Riccardia palmata

1. Monoicous

 

2. Synoicous or paroicous, i.e., antheridia and archegonia developing on same fertile branch.

 

3. Oil-bodies 2--15 per cell; paroicous, with antheridia usually in chambers in proximal part of sexual branches, and archegonia in distal part of same branches 2. Riccardia jugata

3. Oil-bodies 1(--2) per cell, but mainly absent from epidermal cells; synoicous, with antheridia and archegonia usually mixed in a chamber at the tip of sexual branches 4. Riccardia multifida (in part)

 

2. Autoicous, i.e., antheridia and archegonia developing on different fertile branches.

 

4. Epidermal and hypodermal cells with 3--10 oil-bodies 6. Riccardia stricta

4. Epidermal or hypodermal cells with 1--2 oil-bodies.

 

5. Oil-bodies 1--2 in most epidermal and marginal cells 1. Riccardia chamedryfolia

5. Oil-bodies absent from most epidermal and marginal cells (abundant or rare in hypodermal cells).

 

6. Thallus segments with distinct hyaline wings, branches with 1-stratose margins 2-5 cells wide, main axis with 1-stratose margins 1--2(--3) cells wide; oil-bodies abundant in hypodermal cells 4a. Riccardia multifida (in part)

6. Thallus segments lacking distinct hyaline wings, branches and main axis with 1-stratose margins 1(--2) cell wide; oil-bodies rare or absent in hypodermal cells 3. Riccardia latifrons

 

 

1. Riccardia chamedryfolia (Withering) Grolle, Trans. Brit. Bryol. Soc. 5: 772. 1969

Jungermannia chamedryfolia Withering, Bot. Arr. Veg. Gr. Brit. 2: 699. 1776;

Riccardia chamedryfolia fo. major (Lindb.) Schljakov

 

Thallus 1--3(--4)-pinnate, 10--40 x 0.2--2 mm, attenuated proximally; branches polymorphic, lingulate, often dilated and rounded distally, lacking clear continuous and translucent margins but sometimes with 1-stratose margins 1(--3) cells wide; 1--2(--5) oil-bodies present in marginal and costal cells of epidermis, but absent in some cells, 6--36 µm wide. Specialized asexual reproduction rare, by 2-celled endogenous gemmae. Sexual condition autoicous. Spores 13--16 µm.

 

Rocky or organic substrates, wet and shaded habitats, such as along running or standing water, or in swamps, sometimes submerged. ; low to high elevations; Greenland; Alta., B.C., N.S., Ont., Que.; Alaska, Ark., Calif., Conn., Fla., Ga., La., Mass., Miss., N.J., N.Y., N.C., Oreg., Pa., R.I., S.C., Tenn., Va., Wash., W.Va., Eurasia, Africa; Atlantic Islands.

 

Riccardia chamedryfolia is a variable species that is most likely to be confused with Riccardia multifida. The two taxa often grow together on damp litter in Thuja swamps. In addition to oil-bodies and sexual condition, the most obvious characters separating the two species are as follows: Riccardia chamedryfolia has branches that are dilated distally, attenuated proximally, without clear and continuous 1-stratose margins, while Riccardia multifida has branches that are somewhat attenuated distally, with clear and continuous 1-stratose margins. However, some plants do not show these characters clearly, so dried or otherwise dead material of such specimens cannot be identified with confidence. The North American distribution of Riccardia chamedryfolia is here described from herbarium material and literature. The species is probably in fact much more widespread.

 

2. Riccardia jugata R. M. Schuster, J. Hattori Bot. Lab. 62: 305. 1987

 

Thallus irregularly 1--2(--3)-pinnate, sometimes appearing subpalmate, main axis 1--8 x 0.6--0.9 mm wide; branches 0.5--0.6 mm wide, short, rounded or dilated distally, bordered by 1 row of cells, some branches linear and elongated; epidermal cells with 2--15 oil-bodies, these small, inconspicuous, 3--9 µm; hypodermal cells with 2--3(--7) oil-bodies, these larger and darker, 4--16 µm. Specialized asexual reproduction infrequent, by 2-celled endogenous gemmae. Sexual condition paroicous. Spores 10--14 µm.

 

Wet and decaying wood, shaded locations; low to moderate elevations; Ga., Ky., N.C., S.C., Tenn.

 

The growth habit of Riccardia jugata can be similar to that of R. latifrons or R. palmata.

 

3. Riccardia latifrons Lindberg, Acta Soc. Sci. Fenn. 10: 513. 1875

 

Thallus irregularly palmate to subpalmate or 1--2-pinnate, 1--8 x 0.5--2 mm, attenuated proximally; branches short-lingulate, rounded or emarginate distally, margins 1--2-stratose; oil-bodies absent from epidermal cells, in some colonies sporadically present in hypodermal cells, then 1(--3) per cell, 7--12 µm. Specialized asexual reproduction frequent, rare or absent, when present by 2-celled endogenous gemmae. Sexual condition autoicous; spores 14--17 µm.

 

The nearly constant absence of oil-bodies in living material of Riccardia latifrons is a clear indication of its identity. When dry and sterile, it can be confused with Riccardia palmata, which is to be found in the same type of habitats.

 

Subspecies 2 (2 in the flora): Greenland, North America, Eurasia.

 

1. Thallus irregularly palmate to subpalmate; main axis not obvious, branches 0.8--1.0 mm wide, 5--6 cells thick             3a. Riccardia latifrons subsp. latifrons

1. Thallus 1--2-pinnate, main axis obvious, main axis 1.4--1.8 mm wide, 5--9 cells thick      3b.Riccardia latifrons subsp. arctica

 

 

3a. Riccardia latifrons Lindberg subsp. latifrons

 

Thallus irregularly palmate to subpalmate, stolon-like axes lacking or rare. Branches elongate, 0.5--0.7 mm wide, 5--6 cells thick.Specialized asexual reproduction frequent.

 

On damp rotting wood and peat; low to high elevations; St. Pierre and Miquelon; Alta., B.C., N.B., Nfld. and Labrador, N.W.T., N.S., Ont., P.E.I., Que., Yukon; Ala., Alaska, Ark., Calif., Conn., Del.,  Fla., Ga.,  Idaho, , Ill., Ky., La.,  Maine, Md., Mass., Mich., Minn., Miss.,  Mont., N.H., N.J.,  N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., Tenn., Vt., Va., Wash., W.Va., Wis., Wyo.; Bermuda;  Eurasia; Asia; Africa; Atlantic Islands.

 

3b. Riccardia latifrons subsp. arctica R.M. Schuster & Damsholt, Journal of the Hattori Botanical Laboratory 62: 303. 1987.

 

Thallus 1--2-pinnate, main axis obvious, main axis 1.4--1.8 mm wide, 5--9 cells thick Branches short. Specialized asexual reproduction rare or absent.

 

Bogs, fens, on and among Sphagnum colonies; low to high elevations; Greenland; Nfld. and Labrador; Europe.

 

It is at best very difficult, if not impossible, to separate Riccardia latifrons subsp. arctica from Riccardia chamedryfolia when only dried and sterile material is at hand.

 

4. Riccardia multifida (Linnaeus) Gray, Nat. Arr. Brit. Pl. 1: 684. 1821.

 

Thallus regularly (2--)3--4-pinnate, 10--30 x 0.8--1.2 mm, with 1-stratose margins 1--2(--3) cells wide; branches thin, flat, linear, 0.2--0.8 mm wide, parallel-sided and often tapering distally, 1-stratose margins 3--4(--5) cells wide, appearing hyaline and winged; oil-bodies absent from marginal cells and most epidermal cells, sporadically present and solitary in epidermal cells of the costal region; hypodermal cells with 1--2(--4) large oil-bodies. Specialized asexual reproduction infrequent, by 2-celled endogenous gemmae. Sexual condition synoicous or autoicous. Spores 13--16 µm.

 

Subspecies 4 (2 in the flora):  Greenland, North America, Eurasia.

 

1. Autoicous; ultimate segments (3-)4 cells thick medially; 1-stratose margins 2--3(--4) cells wide 4a. Riccardia multifida subsp. multifida

1. Synoicous; ultimate segments 3 cells thick medially; 1-stratose margins 4--5 cells wide 4b. Riccardia multifida subsp. synoica

 

4a. Riccardia multifida (Linnaeus) Gray subsp. multifida

Riccardia multifida var. ambrosioides (Nees) Carrington & Pearson

 

Thallus ultimate segments (3--)4 cells thick medially, with 1-stratose margins 2--3(--4) cells wide. Sexual condition autoicous.

 

Rock, moist litter, humus, shaded locations, commonly Thuja swamps; low to high elevations ; Greenland; Alta., B.C., Man., N.B., Nfld. and Labrador, N.S., Ont., Que., Yukon; Ala., Alaska, Ark., Calif., Conn., Del., Fla., Ga., Idaho, Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Tenn., Tex., Vt., Va., Wash., W.Va., Wis.; West Indies; Europe; Asia Pacific Islands (including New Zealand).

 

Riccardia multifida subsp. multifida is mainly saxicolous, occurring in shaded locations protected from long desiccation periods.

 

 

4b. Riccardia multifida subsp. synoica R. M. Schuster, J. Hattori Bot. Lab. 62: 319. 1987

 

Thallus flat or slightly concave dorsally; ultimate segments 3 cells thick medially, with 1-stratose margins 4--5 cells wide. Sexual condition synoicous, with occasional isolated male and female branches.

 

Usually on decaying wood; low elevations; Fla., Ga., Minn., Miss., N.C., S.C.

 

It is doubtfull that sterile specimens of Riccardia multifida subsp. synoica can be separated from the subsp. multifida.

 

5. Riccardia palmata (Hedwig) Carruthers, J. Bot. 13: 302. 1865

Jungermannia palmata Hedwig, Theoria Generat. 87: 1784

 

Thallus deep green, palmate or subpalmately pinnate, 5--10 x 0.2--0.4 mm, with main part appressed and branches erect. Branches linear and tapered, 0.15--0.3(--5) mm wide, attenuated distally; margins rounded in cross-section, not 1-stratose; oil-bodies 1(--3) per cell, sporadic in epidermal cells, present in most hypodermal cells, 6--15 µm. Specialized asexual reproduction frequent, by (1--)2-celled endogenous gemmae. Sexual condition dioicous. Spores 12--15 µm.

 

Mainly rotting wood, often associated with running water under tree cover, occasionally peat; low to high elevations; Greenland; B.C., N.B., Nfld. and Labrador, N.W.T., N.S., Ont., Que., Yukon; Ala., Alaska, Ark., Calif., Conn., Fla., Ga., Idaho, Ill., Ky., La., Maine, Mass., Mich., Minn., Miss., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Tenn., Vt., Va., Wash., W.Va., Wis., Mexico; West Indies; Bermuda; Eurasia, Atlantic Islands.

 

Because of its similar growth form and habitat preferences, Riccardia palmata is most likely to be confused with Riccardia latifrons, particularly if sexual condition is not observable on the specimen. Additional distinguishing characters are: Riccardia palmata has epidermal cells 20--30 µm wide, with their main axes parallel to the branch margins, while R. latifrons has epidermal cells 35--55 µm wide, with their main axes obliquely pointing toward the margins.

 

6. Riccardia stricta R. M. Schuster, J. Hattori Bot. Lab. 62: 326. 1987

 

Thallus regularly 2--3-pinnate, 10--30 x 0.5--0.8 mm, with 1-stratose margins 2--3 cells wide; branches thin, flat, linear, 0.4--0.6 mm wide, parallel-sided and often tapering distally, with 1-stratose margins 2--6 cells wide, appearing hyaline and winged; oil-bodies present in hypodermal and epidermal cells, including marginal cells, 3--6(--10) per cell, 5--14(--20) µm. Specialized asexual reproduction abundant, by 2(--3)-celled endogenous gemmae. Sexual condition autoicous. Spores 10--12 µm.

 

Rotting wood, humus, soil and rock ledges, in moist locations; low elevations; Ala., Fla.

 

The growth habit of Riccardia stricta is very similar to that of R. multifida. Oil-bodies and sexual condition must be observed for a positive separation of the two taxa.

 

Excluded Species:

 

Riccardia incurvata Lindberg

R. M. Schuster (1992) tentatively mentioned a specimen of Riccardia incurvata from Oregon, but the material has been revised to Riccardia chamedryfolia. Riccardia incurvata is thus considered to not occur in the flora area.

 

 

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SELECTED REFERENCES

Schuster, R. M., 1992. The Hepaticae and Anthocerotae of North America east of the hundredth meridian, Volume V. Field Museum of Natural History, Chicago.