BFNA Title: Blepharostomataceae
Date: S. Jessup
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
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Steven L. Jessup


Plants sparsely intermingled with other cryptogams or forming mats or minute turfs. Branches usually lateral-terminal, the branch replacing ventral lobe of lateral leaf, intermittently lateral-intercalary; flagelliform shoots absent. Leaves alternate, transversely inserted, reduced to 1--4 subequal uniseriate lobes (segments) per leaf; lamina vestigial, reduced to proximal half of cells at the extreme base of leaf lobes; underleaves similar to leaves. Rhizoids sparse or absent, scattered or in small patches proximal to underleaves. Specialized asexual reproduction via unicellular propagules developing on apical leaves from leaf tips, dispersing by separation of transverse cell walls. Gynoecia terminal on leading shoots or dominant lateral branches; subtending branch innovations absent. Perianth subtended by closely imbricate bifurcate uniseriate bracts, tube free at base, cylindrical, weakly clavate, emergent from bracts in distal half, trigonous at apex; perianth mouth contracted, margin ciliate with simple or basally forked uniseriate laciniae.


Genus 1, species 4 (2 species in flora): North America, Mesoamerica, South America, Eurasia, Indonesia, Melanesia, Africa, Atlantic Islands, Pacific Islands


Parallel evolutionary reduction and convergence to simple stem morphology obscures phyletic descent of several lineages in Jungermanniales. Blepharostoma, among other neotenous Jungermanniales, has a long history of taxonomic confusion (R. M. Schuster 1966). Blepharostoma has been variously ranked as a monogeneric subfamily among similarly reduced lineages in both Trichocoleaceae Nakai (R. M. Schuster 2000) and Pseudolepicoleaceae Fulford and J. Taylor (J. Engel and D. Glenny 2008), or included with Lophochaete in a separate family Blepharostomataceae Müll Frib, emend. Schuster (K. Damsholt 2013). Lophochaete, previously subsumed in Pseudolepicolea, is now recognized as sister lineage to Anthelia in Antheliaceae (suborder Jungermanniinea).



SELECTED REFERENCES                      


Damsholt, K. 2013. Blepharostomataceae. In: The Liverworts of Greenland. Nord. Bryol. Soc. Lund., pp. 30--36.  Engel, J. and D. Glenny, 2008. A Flora of the Liverworts and Hornworts of New Zealand, Vol. 1. Missouri Botanical Garden Press. Schuster, R. M. 1966. Blepharostomaceae. In: Hepaticae and Anthocerotae of North America East of the Hundredth Meridian. New York. Vol. 1, pp. 722--753.  Schuster, R. M. 1988. The Hepaticae of South Greenland. Beiheft zur Nova Hedwigia 92: 1--225.  Schuster, R. M. 2000. Austral Hepaticae Part I. Beih. Nova Hedwigia 118: 1--524. Schuster, R. M. and K. Damsholt 1974. The Hepaticae of West Greenland from ca. 66° to 72°N. Meddelel. om Grønland 199: 1--370.  Söderström, L., A. Hagborg, M. Konrat et al. 2016. World checklist of hornworts and liverworts. PhytoKeys 59: 1–828.


1. BLEPHAROSTOMA (Dumortier) Dumortier, Recueil Observ. Jungerm., 18. Tourney. 1835.  [Greek blépharon, eyelid, and stoma, mouth, ciliate margin of perianth mouth resembles eyelids with long eyelashes.]


Plants pale green, yellow-green to verdant; leafy shoots tristichous, isophyllous to subisophyllus, 0.4--2 cm long, 0.7--1 mm wide.  Stems prostrate, procumbent, ascending; irregularly and remotely to closely branched; hyalodermis absent; cortical cells (10-- 18--30 x (28--)30--70 \um, 8--12 cells in cross-section; cortical cell walls thin; medullary cells 3--6 in cross-section, smaller than cortical cells. Leaves distant to imbricate at shoot apices; lobes reduced to (1--2)3--4 subequal uniseriate segments, spreading-arching; leaf segments 7--14(--16) cells long, gradually tapering or blunt, sporadically or frequently forked once below middle; leaf segments 100--400 \um long at shoot base, 300--650 \um at apex of mature shoots; underleaf segments frequently one fewer and shorter than lateral leaf segments; leaf base not decurrent; trigones absent (transverse walls in leaf segments sometimes thickened externally); oil bodies globular, minutely segmented, 2--4(--6) \um, 2--8 per cell. Sexual condition autoicous, paroicous (reputedly pseudodioicous). Androecia short terminal spikes on leading shoots or lateral branches, becoming intercalary below gynoecia; bracts similar to leaves; bract segments often bifurcate below middle; lamina extending 2 cells above leaf insertion; bract pairs 2--10, imbricate; antheridia 1 or 2 per fertile bract; antheridium stalk uniseriate. Gynoecia bracts and bracteoles imbricate, appressed, free at base, 3-ranked, enlarged toward apex; uniseriate lobe segments bifurcate from below middle, lamina extending 3--4 cells above leaf insertion, sheathing perianth base. Perianth (1.4--) 2 mm long at maturity, unistratose in upper half, 2 or 3-stratose at base; uniseriate laciniae to 200 \um long, composed of (3--)5---8 (--12) cells. Perigynium absent, stem apex forming a shoot calyptra, 4--8 archegonia enclosed by each perianth, the undeveloped archegonia becoming lateral on developing shoot calyptra. Seta diameter 100--175 \um; outer cell rows 8; inner cells 4. Capsules purple-brown, ovoid to ellipsoidal; wall 2-stratose; outer cells bearing red-brown nodular thickenings on longitudinal and transverse radial walls, inner cells bearing semiannular thickenings on longitudinal and transverse radial walls and scalariform thickenings on tangential walls. Spores 8--16 \um; brown; minutely rough vermiform texture. Elaters red-brown, straight or slightly curved, gradually tapered to blunt; elater width 8--16 \um, length 130--300 \um; spiral bands 2; band width 2 \um.


Species 4, (2 species in the flora), moist decomposing wood, soil, rocks, bark.


Blepharostoma shows a continuum of phenotypic variation in response to microenvironmental conditions. Distinguishing species, subspecies, and varieties is problematic where overlapping ecophenotypic variation obscures divergent character states. W. C. Steere and H. Inoue (1978) observed a continuum of overlapping variation in diagnostic characters separating B. trichophyllum subsp. brevirete and B. trichophyllum subsp. trichophyllum in specimens from Arctic Alaska where Blepharostoma is ubiquitous. Blepharostoma arachnoideum likewise bears a history of taxonomic uncertainty (D. H. Wagner 2011). The taxa traditionally recognized in North American Blepharostoma are treated here.




Hollensen, R. H. 1964. The morphology of Blepharostoma trichophyllum (L.) Dumort. J. Hatt. Bot. Lab. 27: 159--177.  Steere, W. C. and H. Inoue. 1978. Hepaticae of Arctic Alaska. J. Hattori Bot. Lab. 44: 251--345.  Wagner, D. H. 2011. Observations on Blepharostoma arachnoideum (Pseudolepicoleaceae) of western North America. Bryologist 114: 696--701.


1.  Plants terrestrial; leaf segments typically 3 or 4; cells at center of leaf segments less than 60 \um average length; branched leaf segments infrequent or absent on most vegetative shoots, restricted to gynoecial and androecial bracts; gemmiparous leaf segments present or absent; transverse cell walls in leaf segments thickened, sometimes protruding; dry plants not completely contorted by collapsed cell walls.  …………..1. Blepharostoma trichophyllum


1.  Plants amphibious; leaf segments typically 2 or 3; cells at center of leaf segments more than 60 \um average length; branched leaf segments frequent on most vegetative shoots, not restricted to gynoecial and androecial bracts; gemmiparous leaf segments present; transverse cell walls in leaf segments uniformly thin, not protruding; dry plants completely contorted by collapsed cell walls. ………………..…2. Blepharostoma arachnoideum


1. Blepharostoma trichophyllum (Linnaeus) Dumortier, Recueil Observ. Jungerm., 18, 1835


Jungermannia trichophylla Linnaeus, Sp. Pl. 1: 1135. 1753


Plants terrestrial; dry plants minimally contorted. Leaves distant to congested below apex, divided into (1--)2--4 segments; segments branched infrequently on mature shoots. Leaf cells quadrate to long-rectangular; longest cells in leaf segments 0.8--4 times cell width; transverse cell walls thickened, protruding or not protruding at leaf surface; central cells in segments less than 60 \um average length.


Subspecies 2 (2 in the flora): Greenland; Canada; United States; Mexico; Central America; South America; Eurasia; Indonesia; Melanesia; Africa; Atlantic Islands; Pacific Islands.


Blepharostoma trichophyllum subsp. trichophyllum encompasses a widely distributed complex of fertile and sterile ecophenotypes and regional strains isolated by distance and insular microhabitats. Phenotypes occurring in harsh Arctic and high elevation environments are recognized as B. trichophyllum subsp. brevirete.


1. Length of longest cells in leaf segments 2--4 times cell width; transverse cell walls of leaf segments protruding at leaf surface; lateral intercalary branches infrequent; cells in stem cortex 10--18 \um; oil bodies 4--8 per cell; spores 8--12 \um. ……..1a. Blepharostoma trichophyllum subsp. trichophyllum


1. Length of longest cells in leaf segments 0.8--2 times cell width; transverse cell walls of leaf segments not protruding at leaf surface; lateral intercalary branches frequent; cells in stem cortex 18--23 \um; oil bodies 2--5 per cell; spores 12--16 \um. ……..1b. Blepharostoma trichophyllum subsp. brevirete


1a. Blepharostoma trichophyllum subsp. trichophyllum


Stem branching predominantly lateral-terminal, infrequently developing lateral-intercalary branches; cells in stem cortex 10--18 \um. Leaves below apex bearing (1--3) --4 segments. Leaf cells rectangular, longest cells in leaf segments 2--4 times cell width; central cells in segments less than 60 \um average length; transverse cell walls of leaf segments protruding at leaf surface; oil bodies 4--8 per cell.  Specialized asexual reproduction present or absent; gemmae, when present, developed sporadically toward apex on some mature shoots. Spores 8--12 \um.


Eecaying wood, soil, stream banks, spray zones, shaded ledges, boles and tree limbs, dripping crags and rock crevices; at southern range limits restricted to small insular microhabitat refugia, mountain tops, shaded rock in canyons near cool flowing water; 0--4000 m: Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Conn., D.C., Ga., Idaho, Ill., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mont., Nev., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., S.C., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Central America; South America; Europe; Asia; Africa; Atlantic Islands (Iceland, Azores); Pacific Islands (Hawaii).


Blepharostoma trichophyllum subsp. trichophyllum inhabits diverse microhabitats in perennially cool-moist environments, and expresses a corresponding complexity of phenotypic variation, from pale attenuated forms with distant leaves reduced to 1--2 short segments, sparsely intermingled among other cryptogams, to verdant profusely branching robust forms having densely imbricate leaves uniformly bearing 3--4 long segments, forming pure miniature turfs. Nutrient limitation and deep shade contribute to the ontogeny of highly reduced phenotypes. Blepharostoma trichophyllum subsp. trichophyllum is likely paraphyletic relative to segregate taxa described in Blepharostoma.


1b. Blepharostoma trichophyllum subsp. brevirete (Bryhn & Kaalaas) R .M. Schuster, Bull. Natl. Mus. Canada 164: 16, 1959


Blepkharostoma trichophyllum var. brevirete Bryhn & Kaalaas, Bryoph. Itin. Pol. Norv., 46. 1906 [1907].


Stem branching predominantly lateral-terminal, frequently developing lateral-intercalary branches; cells in stem cortex 18--23 \um. Leaves below apex bearing (1--)2--3 (3--4) segments; segments branched infrequently, or segment branches absent on mature shoots. Leaf cells quadrate to rectangular, longest cells in leaf segments 0.8--2 times cell width; central cells in segments less than 60 \um average length; transverse cell walls of leaf segments not protruding at leaf surface; oil bodies 2--5 per cell. Specialized asexual reproduction absent. Spores 12--16 \um.


Moist microhabitats buffered against desiccation in polar and arctic-alpine environments, early snow-melt zones, crevices, windy barrens and drainages; 0--4000 m: Greenland; Alta. B.C., N.W.T., Nunavut, Que., Yukon; Alaska, Montana; Europe; Asia; Atlantic Islands (Iceland).


Blepharostoma trichophyllum subsp. brevirete is ubiquitous at northern latitudes, extending to the northern limits of cryptogam habitat, occurring as isolated shoots, dominant or codominant in mats with diverse liverworts, mosses, and lichens. The subspecies brevirete is propagated by dispersal of vegetative fragments. Plants do not develop gemmiparous leaf segments and are usually sterile. Blepharostoma trichophyllum subsp. trichophyllum is absent or very rare over much of the range of B. trichophyllum subsp. brevirete. Specimens intermediate in some or all diagnostic characters are often encountered. Blepharostoma trichophyllum subsp. brevirete is apparently an adaptive ecophenotype derived from B. trichophyllum subsp. trichophyllum.



2. Blepharostoma arachnoideum M. Howe, Mem. Torrey Bot. Club 7: 140, 1899  E


Plants amphibious; dry plants extremely contorted. Leaves usually distant below apex, divided into (1--)2---3(3--4) segments; segments branched frequently on mature shoots. Leaf cells rectangular; longest cells in leaf segments about 2 times cell width; transverse cell walls thin, not protruding at leaf surface; central cells in segments more than 60 \um average length. Specialized asexual reproduction present; gemmiparous leaf segments frequent, regularly developed near apex on all mature shoots.


Wet and perennially moist microhabitats, cold, shaded, low energy spray, drip and splash zones; headwaters in steep ravines, or submerged in cold ultraoligotrophic lakes; attached to decomposing wood, rock, compact saturated gravel and soil; 0--2100 m: Alta., B.C., Alaska, Calif., Oreg., Wash., Nev.


Blepharostoma arachnoideum is known from few localities and is considered rare. The plants are amphibious or aquatic, inconspicuous, occurring in widely scattered small patches of sterile plants. Fertile female plants of B. arachnoideum, described from a single specimen, have cells in the perianth tube larger and number of cells in the laciniae fewer than B. trichophyllum subsp. trichophyllum (D. H. Wagner, 2011). Androecia and sporophytes of B. arachnoideum are unknown. Blepharostoma arachnoideum has a distinctive lax morphology when wet and contortion when dry. Blepharostoma arachnoideum is plausibly interpreted as an example of amphibious polymorphism, analogous with attenuate heterophyllous phenotypes developed in aquatic mosses and other liverworts. A disjunct population of aquatic B. arachnoideum occurs in the deep benthic flora of Lake Tahoe, Nevada.


Blepharostoma trichophyllum and B. arachnoideum are rarely observed intermixed in the same microhabitat. In wet microhabitats, Blepharostoma trichophyllum often has weakly developed cell walls in early growth from sporelings, and specimens appear similar to phenotypes of B. arachnoideum. Branched leaf segments and gemmiparous leaf segment apices are typically present on all leading shoots of Blepharostoma arachnoideum, whereas gemmiparous leaf segments do not develop in B. trichophyllum subsp. brevirete. Blepharostoma trichophyllum subsp. trichophyllum produces branched and gemmiparous leaf segments sporadically, but in B. trichophyllum subsp. trichophyllum transverse cell walls are thickened along the sides of the leaf and protrude at the leaf surface, whereas B. arachnoideum has uniformly thin cell walls that do not protrude.