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BFNA Title: Leptodictyum |
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LEPTODICTYUM -
Amblystegiaceae XXX. LEPTODICTYUM (Schimper) Warnstorf,
Kryptogamenfl. Brandenb., Laubm., 867. 1906 * [Greek lepto, thin or fine, alluding to the fine outline of the leaf
cells] S.
G. Newmaster Amblystegium subgen Leptodictyum Schimper, Syn. Musc. Eur., 595. 1860
Plants medium-sized, green,
yellow-green, brown-green, in
thin, loose to dense mats. Stems prostrate,
irregularly to subpinnately branched, without a
hyalodermis; epidermal
cells small and thick-walled; pseudoparaphyllia foliose, lanceolate; rhizoids
or rhizoid initials on stem or at abaxial leaf costa insertion, smooth,
slightly branched. Stem and branch leaves similar, erect-spreading, not secund,
somewhat complanate, oblong-lanceolate, acute or acuminate, not plicate,
nondecurrent; marginal lamina cells 1-stratose, margins plane, entire or
serrulate; costa single, ending in distal half before the apex; median lamina
cells linear, smooth, thin- to thick-walled; alar cells enlarged,
rectangular, thin walled, not extending up the leaf, not decurrent. Specialized
asexual reproduction lacking. Sexual condition autoicous. Perichaetial
leaves lanceolate, acuminate, erect, margin entire; lamina cells smooth. Seta
single, elongate, smooth. Capsule cylindrical, inclined to
horizontal, curved, contracted below mouth; annulus of 2--3 rows of large,
deciduous cells; operculum conic, apiculate; peristome perfect, yellow to
brown; endostome hyaline, filiform, cilia 1--4, nodulose. Calyptra
cucullate, naked. Spores globose to ovoid, yellow to yellow-brown, minutely
papillose, 10--15 \um. Species 7 (2
in flora): circumtemperate. L. Hedenäs
(2003) included in this genus only a single, variable species, Leptodictyum riparium, with L. humile treated in Amblystegium. According to A. Vanderpoorten et al. (2001, 2002), L. humile
should be treated as a member of Hygroamblystegium.
From a morphological point of view, there is in fact a continuum between Hygroamblystegium humile and H. tenax,
the only actual feature distinguishing the two being the length of the costa,
which continuously varies from ceasing at mid-leaf to percurrent. The most
recent molecular analyses (A. Vanderpoorten, personal commmunication) suggest
that Leptodictyum riparium falls
within a completely unrelated clade together with large Campylium species. A. Vanderpoorten et al. (2002) suggested that Leptodictyum riparium appears more
closely related to Campylium stellatum
and Campyliadelphus chrysophyllus than
to Amblystegium species. Further
molecular evidence is needed to resolve these systematic issues. SELECTED
REFERENCE: Conard, H. S. 1959. Amblystegium. Bryologist 62: 96--104.
Allen, B. and R. E. Magill. 2004. Leptodictyum
wallacei (Musci: Amblystegiaceae), a new species from Syst. Bot. 26:
470--479. Vanderpoorten, A., L. Hedenäs, C. J. Cox, and A. J. Shaw. 2002. Circumscription,
classification, and taxonomy of Amblystegiaceae (Bryopsida) inferred from
nuclear and chloroplast DNA sequence data and morphology. 51: 115--122. 1. Plants flaccid, large, 6--20 cm; leaf basal
cell walls lax, alar cells differentiated...……………………….….. 1. Leptodictyum riparium 1.
Plants stiff, smaller, 3--6 cm; leaf basal cells firm-walled, alar
cells not differentiated…………………..………… 2.
Leptodictyum wallacei 1.
Leptodictyum riparium (Hedwig)
Warnstorf, Kryptogamenfl. Brandenb., Laubm., 878. 1906 Hypnum riparium Hedwig, Sp. Musc. Frond., 241. 1801; Amblystegium brevipes Cardot &
Thériot in Holzinger; A. riparium
var. flaccidum (Lesquereux & T.
P. James) Renauld & Cardot; A.
riparium var. fluitans (Lesquereux
& T. P. James) Renauld & Cardot in Macoun; A. riparium var. longifolium
(Schultz) W. P. Schimper in M. Lange; Amblystegium
riparium (Hedwig) Schimper in B.S.G.; Brachythecium
pennellii E. B. Bartram; Campylium
polygamum var. longinerve
(Renauld & Cardot) Grout; Leptodictyum
brevipes (Cardot & Thériot in Holzinger) Brotherus; L. riparium var. abbreviatum (Schimper in B.S.G.) Grout; L. riparium var. brachyphyllum
(Cardot & Thériot in Holzinger) Grout; L. riparium var. elongatum (Schimper
in B.S.G.) Warnstorf; L. riparium
var. flaccidum (Lesquereux & T.
P. James) Grout; L. laxirete
(Cardot & Thériot) Brotherus; L.
sipho (Palisot de Beauvois) Brotherus; L. vacillans (Sullivant) Brotherus; Rhynchostegiella georgiana Dixon & Grout Stems irregularly branched, in flat, loose, flaccid, long
trailing mats, light green to yellow-brown, 6--20 cm, branches
spreading. Leaves 2.5--6 mm, slightly contorted when dry, erect to wide
spreading or appearing distichous, somewhat complanate especially in
branches, distant, often obliquely attached to stem, broadly short to
gradually long acuminate, costa (45)52.5--114 \um at base, margins entire,
upper cells long, rhomboidal, (34--)42--117 x 7.5--12(--13) \um, basal cell
walls lax, alar cells differentiated, enlarged, rectangular. Seta
8--26 mm, light to dark brown. Capsule 2.2--2.5 mm long, cylindric,
arcuate, brown to reddish brown. Spores finely papillose, 10.5--18.5
\um. Capsules rare.
Humus, logs and tree bases in swamps or wet depressions in forests or aquatic
on rocks in streams and rivers; low to moderate elevations; Greenland; Alta.,
B.C., Man., N.B., Nfld. and Labrador, N.W.T., N.S., Nunavut, Ont., P.E.I.,
Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del.,
Fla., Ga., Ill., Ind., Iowa, Kans., La., Maine, Md., Mass., Mich., Minn.,
Miss., Mo., Nebr., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla.,
Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va.,
Wis., Wyo.; Mexico; Central America; South America; Europe; Asia; Africa;
Indian Ocean Islands; Pacific Islands; Australia. As the
specific epithet implies, Leptodictyum
riparium occurs along rivers, often in flooded areas where it is stranded
on tree bases in hardwood forests. It is sometimes confused with another
wetland species, Drepanocladus aduncus,
which differs in axillary hairs with 1--3 distal hyaline cells. There is
tremendous morphological variability among the North American specimens of Leptodictyum riparium, suggesting the
existence of several ecotypes, which have been erroneously named as many
varieties and forms in Leptodictyum,
Amblystegium, and Campylium. These
synonyms are summarized by A. J. Grout (1928--1934), H. S. Conrad (1959), and
H. A. Crum and L. E. Anderson (1981). 2.
Leptodictyum wallacei
B.H. Allen & Magill, Novon 14: 377, fig. 1. 2004 Stems sparingly branched, in slender, stiff strands, green to
yellow-brown, 3--6 cm, branches spreading.
Leaves 2--2.5 mm, erect to
wide spreading, strongly contorted when dry, often transversely attached to
the stem, gradually long-acuminate; costa 50--75 \um at base; leaf margins
entire or obscurely serrulate; distal laminal cells long, rhomboidal, 70--120
x 6--7 \um, basal cells firm walled, alar cells not differentiated. Sporophytes
not seen. Large
submerged masses, endemic to Hext Spring, San Saba Co., There appears
to be enough morphological evidence to support the recognition of Leptodictyum wallacei, which is
distinguished from the variable aquatic ecotypes of Leptodictyum riparium by its stiff stem, smaller size and absence
of alar cell elaboration. However, Lars Hedenäs (personal communication) has
examined an isotype and suggested that the specimen fits well within the
variation of Leptodictyum riparium.
Further molecular evidence is needed to evaluate the haplotype variation of L. riparium. |