|
BFNA Title: Pleurocladula |
|
PLEUROCLADULA – CEPHALOZIACEAE XX. PLEUROCLADULA
Grolle, J. Bryol. 10: 269. 1979 *
[Greek pleuro side, Greek clado branch; alluding to lateral
branching] David M. Krayesky Jerry G. Chmielewski Pleurocladula º Pleuroclada
Spruce 1882 (nom. illeg.), non Pleurocladia
A. Braun 1855 Plants light pellucid green,
in full sun or shade, nearly white when dry (occasionally reddish
brown). Stem possessing a hyalodermis; Frullania type (lateral-terminal) branching common and lateral-intercalary
branching rare; flagelliform branches occurring in some populations. Leaves
transverse-succubous, not decurrent, distant to imbricate, entire; 2-lobed,
lobes triangular, and concave; oil bodies absent. Underleaves
large, nearly as long as leaves but only half as wide, often possessing 1--2
sub-basal teeth. Specialized asexual reproduction by gemmae uncommon, 1-celled,
spherical to ellipsoidal, at shoot apex.
Sexual condition
dioicous. Androecia intercalary, each bract with basal antical tooth;
antheridia occurring singly per bract, ovoid, with non-tiered jacket cells
and a 2-seriate stalk. Gynoecia terminal, bracteole always
narrower and sometimes shorter than bracts; perianth clavate to oblong or
fusiform, fleshy and multistratose at base, mouth lobate with a crenulate
margin. Sporophyte seta yielding 8--12 epidermal and 5--8 inner cell
rows; capsule ellipsoidal, four valved, capsule wall 2-stratose. Species 1 (1 in the flora): North America, Europe and Asia.
Pleurocladula albescens (Hooker) Grolle and P. islandica (Nees) Grolle have been
treated as separate species (e.g. M. Krzakowa and J. Sweykowski 1981; R.
Grolle 1983). We concur with J. A.
Paton’s (1999) assessment that the genus is monotypic as Paton (1976)
provided ample evidence for the inclusion of P. islandica into synonymy with P. albescens. The status of Pleurocladula
is a point of debate. A. A. Vilnet et
al. (2012) proposed that Cephalozia is polyphyletic forming two
clades. One Cephalozia clade included the generitype, as well as other Cephalozia species. The second clade included species of Cephalozia, Pleurocladula, and Schofieldia. J. Váňa et al. (2013)
have transferred those species in the second clade to Fuscocepaloziopsis. K.
Feldberg et al. (2016) concur with Váňa et al.
(2013). Although the Feldberg et al.
(2016) analysis of the Cephaloziaceae is the most comprehensive molecular
assessment of the group to date, the maximum likelihood value of the Fuscocepaloziopsis clade does not
provide the same level of support as evidenced in the recent treatment of Odontoschisma (S. C. Aranda et al. 2014). For this reason we continue to recognize Pleurocladula, Schofieldia, and Cephalozia
sensu lato as distinct genera. In order to support the reorganization of
these specific Cephaloziaceae taxa into two genera, namely, Cephalozia
and Fuscocephaloziopsis, both an extensive anatomical study and a
molecular evaluation with a very strong level of support will need to be demonstrated,
as is the case with the recent treatments of Odontoschisma (S. C.
Aranda et al. 2014; S. R. Gradstein and A. L.
Ilkiu-Borges 2015). SELECTED REFERENCES Aranda, S.C., S.R. Gradstein, J. Patiňo, B.
Laenen, A. Désamoré, and A. Vanderpoorten.
2014. Crandall-Stotler, B.,
R.E. Stotler, and D.G. Long.
2009. Phylogeny and
classification of the Marchantiophyta.
Edinburgh J. Bot. 66: 155--198.
Feldberg, K., J. Váňa,
J. Krusche, J. Kretschmann, S. D. F. Patzak, O. A. Pérez-Escobar, N. R.
Rudolf, N. Seefelder, A. Schäfer-Verwimp, D. G. Long, H. Schneider, and J.
Heinrichs. 2016. A phylogeny of Cephaloziaceae
(Jungermanniopsida) based on nuclear and chloroplast DNA markers. Organisms Diversity and Evolution 16 [doi:
10.1007/s13127-016-0284-4]. Frye, T. C. and L. Clark.
1943. Hepaticae of North
America. Univ. Washington Publ. Biol.
6(2): 187--190. Geissler, P. and H.
Bischler. 1989. Index Hepaticarum: Vol. 11 Naiadea to Pycnoscenus, J. Cramer,
Berlin, Germany. Gradstein, S. R. and
A. L. Ilkiu-Borges. 2015. A taxonomic monograph of the genus Odontoschisma. Nova Hedwigia 100: 16--100. Grolle, R.
1979. Miscellanea
hepaticologica 171--180. J. Bryol. 10:
263--272. Grolle, R. 1983.
Hepatics of Europe including the Azores: An annotated list of species,
with synonyms from the recent literature.
J. Bryol. 12: 403--459. Hooker,
W. J. 1816. British Jungermanniae. 84 plates and 4 supplementary plates. London.
Krzakowa, M. and J. Szweykowski.
1981. A species concept in the
genus Pleurocladula
(Hepaticae). Acta Soc. Botanic.
Poloniae 39: 465--479. Paton, J.
A. 1976. Pleuroclada
albescens (Hook.) Spruce with gemmae.
J. Bryol. 9: 1--5. Paton, J.
A. 1999. The Liverwort Flora of the British
Isles. Harley Books, Colchester,
England. Schuster, R. M. 1974.
Pleurocladula. In:
R. M. Schuster. The Hepaticae
and Anthocerotae of North America east of the hundredth meridian. New York,
Vol. 3, Pp. 66-6-671. Smith, A. J.
E. 1990. The Liverworts of Britain and Ireland. Cambridge University Press. Cambridge, UK. Spruce, R.
1882. Pleuroclada. In: R.
Spruce. On Cephalozia, its subgenera and some allied genera. Malton, pp. 77--80, Malton. Váňa, J., L. Söderström, A. Hagborg, and M. von Konrat. 2013. Notes on early plants today. 41. New
combinations and synonyms in Cephaloziaceae (Marchantiophyta). Phytotaxa 112: 7--15. Vilnet, A. A., N. A. Konstantinova, and A.
V. Troitsky. 2012. Molecular phylogeny and systematics of the
suborder Cephaloziineae with special attention to the family Cephaloziaceae
s.l. (Jungermanniales, Marchantiophyta).
Arctoa 21: 113--132. 1. Pleurocladula albescens (Hooker) Grolle, J. Bryol. 10: 269. 1979 Jungermannia albescens Hooker, Brit.
Jungermann., pl. 72 and suppl. pl. 4.
1815; Pleurocladula islandica
(Nees) Grolle Plants ca. 4.7--9.4 x 0.2--0.5
mm; prostrate to gregarious, growing in mats, turfs, or singly among other
bryophytes. Stems fleshy 120--185 \um, cortical cells thin walled and 23--39
x 24--39 µm; medullary cells thick walled and 18--24 x 18--22 \um, medulla
112--123 µm in diameter and 5--8 stratose; flagelliform branches occurring in
some populations. Leaves distant to imbricate; erecto-patent; concave; suborbicular
240--397 µm long x 200--400 µm broad; margins entire; 2-lobed, lobes
triangular, incurved; sinus 1/3--1/2 the length of the leaf, base of sinus
rounded to acute; marginal cells 17--31 x 17--31 \um; median cells in lobes
17--26 x 17--35 µm; median leaf cells 17--29 x 23--32 \um; basal cells 23--39
x 23--36 µm. Oil-bodies
absent. Rhizoids scarce to abundant, and abundant on flagelliform
branches, colorless. Underleaves large 273--307 x 99--177
\um; erecto-patent; ovate to sublanceolate; apices acute to obtuse; with or
without basal teeth, often present on one side, occasionally on both. Specialized
asexual reproduction by gemmae 23--26 \um in diameter. Androecia
bracts 0.5--0.6 x 0.4--0.5 mm; in
15--18 pairs; 2-lobed, and with basal antical tooth. Gynoecia
bracts 1--1.3 x 0.9--1.2 mm and bracteoles 0.5--0.6 x 0.4--0.5 mm; in
series of 2; bracts 2-lobed, and much larger than the leaves; bracteoles free
or connate to the base of the bract, unlobed or shallowly 2-lobed with 1--3
teeth. Perianth 1.9--2.9 x 0.8--0.9 mm; clavate to oblong or fusiform;
fleshy and multistratose at base; mouth lobate with a crenulate margin. Seta
250--322 µm in diameter. Capsule 1.1--1.5 x 0.4--0.5 mm,
capsule wall 2 cell layers thick; epidermal cells 15--38 x 22--40 \um;
interior cells 15--20 x 19--76 \um in diameter. Elaters
7--10 µm in diameter, 127--318 µm in length, and (1--)2-spiraled. Spores
brown, vermiculate-verrucose 14--16 \um .
Northern Hemisphere Arctic and temperate (alpine to
montane) areas, on fine to gravelly soils, peaty soils, and rock, and on the
banks of small streams and ephemeral ponds associated with peatland areas;
low to high elevations; Greenland; Alta., B.C., Nfld. and Labr., N.W.T.,
Nunavut, Que., Yukon; Alaska, Calif., Mont., Wash.; Europe; Asia. R. M.
Schuster (1995) indicated Pleurocladula
albescens has a tendency toward being acidophilic. There are some
doubtful records in the United States and these published records will be
treated here as erroneous. These aforementioned
records include: the Wolf and Hall (1878) report from Illinois and the Watson
s.n. 1972 collection in TROPICOS at MO from New Hampshire. The Wolf and Hall (1878) report was treated
by Schuster (1974) as an erroneous, as we have been unable to locate this
collection we continue to follow the Schuster (1974) assessment of this
population. The Watson s.n. 1972
collection from New Hampshire is not Pleurocladula
albescens, but is Orthocaulis kunzeanus
(Huebener) H. Buch. |
