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BFNA Title: Amblystegium |
XX. Amblystegium Schimper, Bryol. Eur. 6:
45. 1853 * [Greek ambly, blunt, and stege, operculum, alluding to obtuse operculum]
Alain Vanderpoorten Plants small and slender in soft mats, green
to yellowish. Stems creeping, freely and irregularly branched; central
strand of small, thin-walled cells present; hyalodermis absent; paraphyllia
none; rhizoids or rhizoid initials only on stem or at abaxial costal
insertion, smooth; axillary hairs with 1(--2) elongate hyaline distal cells.
Stem leaves soft, erect to spreading but never complanate, ovate to
oblong-lanceolate, acuminate, similar to branch leaves although somewhat
larger, not plicate, slightly concave; marginal laminal cells 1-stratose;
margin plane, entire or denticulate; costa 10--30 \um at base, mostly
extending to about mid-leaf but sometimes shorter or reaching 3/4 of leaf
length; median lamina cells firm-walled, slightly incrassate, eporose; alar cells often well differentiated,
sub-quadrate to transversely elongate, in a broadly ovate or transversely
triangular group along margin, reaching from leaf margin ca. 65% of distance
to leaf mid point at insertion, not decurrent. Sexual condition autoicous.
Inner perichaetial leaves narrowing from just before the acuminate
apex, plicate. Capsule 1.5--2 mm, cylindric from a well-developed
neck, strongly curved and inclined to horizontal; peristome perfect; exostome
margin dentate or slightly so. Spores spherical, nearly smooth to
minutely papillose. Species 1 (1
in the flora): widespread in the Holarctic,
reaching into subtropical and tropical areas. Amblystegium differs from Hygroamblystegium
by smaller plant size and a weaker costa, this less than 30 \um wide at base,
most often ceasing at mid leaf. It rarely reaches 3/4 of leaf length but, in
such cases, is straight and not curved as in Hygroamblystegium.
Unlike the latter genus, Amblystegium lacks
paraphyllia. So circumscribed, Amblystegium
is a terrestrial genus that sometimes occurs in swampy but never aquatic or
sub-aquatic habitats. SELECTED REFERENCES
Vanderpoorten A., B. Goffinet, L. Hedenäs, C. J. Cox, and A. J. Shaw. 2003.
A taxonomic reassessment of the Vittiaceae (Hypnales, Bryopsida): evidence
from phylogenetic analyses of combined chloroplast and nuclear sequence data.
Pl. Syst. Evol. 241: 1--12.
1. Amblystegium serpens (Hedwig) Schimper, Bryol. Eur. 6: 53,
pl. 564 (fasc. 55--56. Mon. 9, pl. 3). 1853 Hypnum serpens Hedwig, Sp. Musc. Frond.,
268. 1801; Amblystegium juratzkanum Schimper; A. serpens
var. juratzkanum (Schimper) Rau & Hervey
Stem leaves 0.5--1 mm; median lamina cells shortly
oblong, 12--55 x 7-12 \um, 3--5:1. Seta elongate,
10--25 mm, reddish, smooth. Spores
9--18 \um. Variable
features in A. serpens
include the serration of the leaf border, which ranges from entire to serrulate
or even serrate; length of the costa, from very short (less than 1/5 of leaf
length) to sub-percurrent; the sub-quadrate to transversely elongate shape of
the alar cells; and leaf stance, which ranges from erect to spreading. These
last two characters have sometimes been used to recognize a separate taxon,
var. juratzkanum. The continuous range of variation of these characters, however,
precludes any infraspecific division within A. serpens, which is, overall, a fairly-well
circumscribed species with comparatively low levels of plasticity with regard
to Hygroamblystegium species. Tree trunks,
rotten wood, rock, soil, in a range of habitats from (sometimes salty) swamps
to rather xeric habitats; 0--3000 m; Greenland; Alta., B.C., Man., N.B.,
N.W.T., Nfld and Labr., N.S., Nunavut, Ont.,
P.E.I., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Conn., Del.,
Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Mass., Md.,
Mich., Minn., Miss., Mo., Mont., Nebr., Nev., 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., W.Va., Wash., Wis., Wyo.; Mexico; Central America; South America;
Europe; Asia; North Africa; Australia; Pacific Islands (New Zealand). |