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BFNA
Title: Pleuroziaceae |
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XX. PLEUROZIACEAE Müll. Frib Barbara M. Thiers Plants forming
thick mats or wefts or spreading from substrate, rhizomatous branch system present; branches from axils of
leaves; without flagella. Leaves
alternate, succubous, deeply concave, 2-lobed, the lobes sharply folded
together and usually strongly dimorphic; underleaves
absent. Rhizoids restricted to stem bases. Specialized asexual reproduction
absent. Androecia on short
branches, 1 antheridium per bract. Gynoecium terminal on a short branch, subtended by a single
bract. Perianth
without subfloral branches, well developed, ovoid, narrowed to
mouth, plicate, perigynium absent. Sporophytes robust. Seta short, composed of numerous cell
rows with no detectable pattern of layering.
Capsule subspherical
to ovoid, wall 6--8 cell layers thick, outermost cells with nodular
thickenings along adjacent cell walls; innermost cell layer covered with
fenestrate secondary thickenings; valves straight, divided to base. Elaters 2-spiral, brown. Spores
covered with crowded spines. Genera 1, species 11 (1 species in the flora): Canada;
Central America; South America; Eurasia; Africa; Atlantic Islands (including Macaronesia); Indian Ocean Islands; Pacific Islands
(including Hawaii and New Zealand); Australia. Pleuroziaceae is the sole member of the Pleuroziales Schljakov, and
phylogenetically is quite isolated from other hepatics. Although characterized by
well-differentiated stems and leaves, Pleuroziales
are placed in the Metzgeriidae based on molecular
data, as sister group to the rest of the simple thalloid hepatics
(Crandall-Stotler et al. 2000, 2009). 1. PLEUROZIA
Dumortier, Recueil Observ. Jungerm. 15.
1835 * [Greek pleuron
or rib, sharply folded lateral leaves give ribbed appearance] Barbara M.
Thiers Plants wine-red. Stem
epidermis 1--4 cell rows wide, cortex 8--15 cells wide. Leaves when entire broadly ovate to orbicular, apex rounded,
margins entire, base rounded to cordate; bilobed leaves with ventral lobes ovate
to orbicular, concave, margins entire to undulate and/or dentate near apex,
apex entire, irregularly dentate or shallowly 2-lobed; dorsal lobules
tubular, opening restricted to an aperture complex positioned on adaxial
surface near apex or mid portion of lobule, access to lobule interior
controlled by a hinged, spathulate valve that fits into a concave abutment,
valve and abutment oriented toward lobule base, situated in a weakly to
well-defined oblong or circular basin bordered or overarched by a rounded
lip; lobule attached to lobe for 0.3 or less of lobule length. Oil
bodies colorless, granular, 18--28 per cell. Androecia
bracts in 4--10 pairs. Gynoecial bract 3-lobed, obdeltoid,
lobes triangular; perianth mouth
ciliate, cilia of 3--10 cells, sometimes articulate or branched. Spores
25--50 µm diam., spherical, golden brown. Species 11, 1 in
the flora: Canada; Central America; South America; Eurasia; Africa;
Atlantic Islands (including Macaronesia); Indian
Ocean Islands; Pacific Islands (including Hawaii and New Zealand); Australia. SELECTED REFERENCES Crandall-Stotler et al., 2000. Morphology and
classification of the Marchantiophyta. In: Shaw, A. J. & B.
Goffinet. (eds). Bryophyte Biology, pp. 21--70.Cambridge: Cambridge University Press. Schuster, R. M. 1965. Studies on Hepaticae. XVI. The morphology and systematic
position of the suborder Pleuroziinae. Transactions of the British Bryological
Society 4: 794-800. Thiers, B. M.
1992. A monograph of Pleurozia
(Hepaticae: Pleuroziaceae). Bryologist 96: 517--554. Wang, B. J. et al., 2009. The complete mitochondrial genome sequence
of the liverwort Pleurozia purpurea
reveals extremely conservative mitochondrial genome evolution in liverworts.
Current Genetics 55: 601--609. 1. Pleurozia purpurea Lindb., Acta Soc. Fauna Fl. Fenn. 1 (2): 27. 1877 Plants to 8 cm long,
2--3.5 mm wide; elongate stems sparsely branched. Leaves
when entire restricted to branch bases, 0.2--0.3 x 0.1 mm, margins
short-ciliate near apex; saccate-lobuled leaves dominant on all stems; ventral lobes 2--3
x 1.5--3.5 mm, strongly concave, apex 2-fid to ca. 0.2 leaf length, margins
coarsely dentate at apex; cells of leaf apex quadrate, 25--50 x 25--38 \um,
cells at midleaf quadrate to rectangular, 25--40 x 25--38 \um, cells of leaf
base rectangular, 50--88 x 25--30 µm; dorsal lobules ovoid to deltoid, curved
somewhat toward stem, 1--2 x 1--2 mm, attachment to ventral lobe extending
0.5--0.75 \um, aperture at mid length
of lobule, situated in an oblong basin oblong, lip present on proximal border
of basin, only slightly overarching it.
Sexual condition dioicous. Androecia
bracts spathulate. Gynoecia when fertile lacking
innovations, bracts 2--3 x 2.5--3 mm, lobes extending 0.20 bract length or
less, apices acutely rounded, margins dentate. Perianth plicate in distal half, apical cilia short, with
frequent articulations. Terrestrial in bogs
or other wet habitats in coastal areas; B.C., Alaska; Europe (Britain, Norway
and Denmark); Asia (Bhutan, India, Nepal). Pleurozia purpurea was placed by B. M. Thiers (1992) in subgenus Constantifolia. If examined only superficially, P. purpurea might be confused with members of the Jungermanniaceae such as Anastrophyllum or Jamesoniella, which also has reddish secondary pigmentation and plicate perianths. However, Pleurozia purpurea is a much larger plant, and the structure of the bilobed leaves, with saccate dorsal lobes, is like no other species in North America. The distichous leaf arrangement, absence of underleaves, and the single gynoecial bract surrounding the gynoecium are also diagnostic. |
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