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Pohlia Hedwig, 1801.

Pohlia differs from most species of Bryum (in the broad sense) in having no trace of a limbidium and in the median cells being longer and usually more thick-walled than those of Bryum. The thick-walled feature of Pohlia is emphasized in the pattern of toothing of the leaf margins. The toothing of Bryum is generally formed primarily from lumen extensions with the cell walls of the teeth not significantly thickened toward the tooth apex. The toothing of Pohlia is, in large part, formed with extra thickening of the wall especially in the region of the tooth apex. For this feature of toothing by wall thickening, we use the prefix "crassi-" before the words serrate, dentate, etc. It is important that this distinction be recognized because "crassi-serrate" cells are perfectly correlated in the Bryales with the capacity to produce prorate cells in the lamina. In this connection, it is interesting that close examination of Pohlia, unlike Bryum, will usually show some prorations on distal laminal cells. Another feature of Pohlia that suggests placement in the Mniaceae is the prominent pattern of leaf buttressing, which shows itself in shelf-like prominences on the stem after the leaves are removed. These prominences can be viewed in thin longitudinal sections of the stem and they are generally more than one cell in thickness. The pattern of leaf buttresses shown in Pohlia is also shown in such other Bryalean moss families as Mniaceae, Bartramiaceae and Aulacomniaceae, but not in Bryaceae.

Key to Pohlia Etc.

Mosses treated in this section are unicostate acrocarps with capsules cylindric, often long, inclined to pendent, occasionally erect.

Species included in this key are in Mniaceae, except Anomobryum (Bryaceae), Discelium (Disceliaceae), and Leptobryum (Meesiaceae):
Anomobryum julaceum (Schrader ex P. G. Gärtner, B. Meyer & Scherbius) W. P. Schimper
Discelium nudum (Dickson) Bridel
Epipterygium tozeri (Greville) Lindberg
Leptobryum pyriforme (Hedwig) Wilson
Pohlia andalusica (Höhnel) Brotherus
Pohlia annotina (Hedwig) Lindberg
Pohlia bolanderi (Lesquereux) Brotherus
Pohlia camptotrachela (Renauld & Cardot) Brotherus
Pohlia cardotii (Renauld) Brotherus
Pohlia cruda (Hedwig) Lindberg
Pohlia drummondii (C. Müller Hal.) Andrews in Grout
Pohlia elongata Hedwig
Pohlia filum (W. P. Schimper) Mårtensson
Pohlia flexuosa Harv., recognized from CA since 2004
Pohlia lescuriana (Sullivant) Ochi
Pohlia longibracteata Brotherus in Röll
Pohlia ludwigii (Sprengel ex Schwägrichen) Brotherus
Pohlia nutans (Hedwig) Lindberg
Pohlia obtusifolia (Villars ex Bridel) L. Koch
Pohlia pacifica A. J. Shaw
Pohlia proligera (Kindberg) Brotherus
Pohlia robertsonii Shevock & A. J. Shaw, recognized from CA since 2004
Pohlia sphagnicola (Bruch & W. P. Schimper) Lindberg & Arnell, not known from CA
Pohlia tundrae A. J. Shaw
Pohlia vexans (Limpricht) H. Lindberg, not known from CA
Pohlia wahlenbergii (Weber & D. Mohr) Andrews in Grout

A. Stems inclined with dorsi-ventral arrangement of leaves such that dorsally inserted leaves are smaller and more narrow than ventrally inserted ones; leaves typically with some hint of a limbidium .....Epipterygium: E. tozeri
A. Stems with overall erect arrangement without dorsi-ventral heterophylly; leaves typically without a limbidium .....B

B. Leaves deeply concave with the apex broadly obtuse; leafy stems pale and glossy; cells with the walls thick and pitted .....Anomobryum: A. julaceum
B. Leaves various, keeled or not but never deeply concave; apices acute to acuminate or bluntly obtuse; leafy stems greenish and not glossy; cell walls not thick and pitted .....C

C. Costa filling more than 1/3 of leaf base, becoming excurrent and filling leaf apex; axillary hairs with vividly reddened basal cells .....Leptobryum: L. pyriforme
C. Costa more narrow, excurrent or shorter; axillary hairs without such prominently colored basal cells .....D

D. Plant almost stemless with costa percurrent but disappearing near its base; seta erect and red-brown bearing a slightly inclined short cylindric capsule .....Discelium: D. nudum
D. Plant with a stem 1 mm long or more; costa various but present to leaf base; seta and capsule various .....E

E. Plants commonly with gemmae in the axils of the upper leaves; exothecial cells short-rectangular 1.5-2.5:1; capsules short, less than 2:1 .....F
E. Plants without axillary gemmae; exothecial cells isodiametric or longer than 3:1 .....L

F. Gemmae l or at most 2 per leaf axil .....G
F. Gemmae clustered, more than 3 per leaf axil .....H

G. Leaves spreading, more or less carinate; propagula 2-4:1, with leaf primordia on their mid-regions as well as their Apices .....Pohlia drummondii
G. Leaves erect, not carinate; propagula 1-2:1 with leaf primordia restricted to their apices .....Pohlia filum

H. Propagula less than 2:1 with their leaf primordia only 1-2 cells, curled over the propagulum apex, and with those propagula short-stalked .....Pohlia camptotrachela
H. Propagula elongate, usually more than 6:1; leaf primordia erect to spreading, triangular and multicellular, sometimes absent; propagula stalked or not .....I

I. Leaf primordia on propagula triangular and foliose .....J
I. Leaf primordia absent or small geniculate to spreading peg-like structures .....K

J. Area of leaf primordia occupying only 1/3 to 1/4 of total gemma length of the elongate gemmae .....Pohlia tundrae
J. Area of leaf primordia occupying almost 1/2 of the length of the short oblong gemmae .....Pohlia andalusica

K. Propagula usually with more than 2 erect leaf primordia; plants not glossy .....Pohlia annotina
K. Propagula without leaf primordia or, at most, with 1-2 often geniculate structures .....Pohlia proligera

L. Leaf apices somewhat cucullate at least on upper portions of stem; lower leaves on stem usually black; plant of seepages in snow-melt areas of high mountains .....Pohlia obtusifolia
L. Leaf apices not cucullate; plant and leaves never blackened; plant of various habitats .....M

M. Vegetative leaf margins recurved at least near the base .....N
M. Vegetative leaf margins plane .....P

N. Capsules ovoid, less than 1.5:1, with little definition of a neck; plant usually with nearly spherical, multicellular rhizoidal gemmae slightly buried or surficial near base of stem .....Pohlia lescuriana
N. Capsules pyriform to cylindrical, about 2:1; gemmae unknown in California .....O

O. Plant glaucous, tufted on seepages over schistose rocks, mostly on road cuts; peristome with exostome absent and endostome papillose .....Mielichhoferia: various species
O. Plant green to yellow green; growing on moist soil in alpine areas; exostome and endostome present but without endostome cilia .....Pohlia cardotii

P. Plants paroicous (look for perigonia in axils of leaves immediately below perichaetia) .....Q
P. Plants dioicous .....S

Q. Plants with a white but very glossy cast; leaves erect and overlapping, often appearing almost complanate; walls of median cells thin .....Pohlia cruda
Q. Plants without a whitish cast; cell walls more than 2 µm thick .....R

R. Endostome segments perforate along the keel with the perforations 2-4:1; cilia present; broadly distributed species both in substrate and elevational occurrence, often in ruderal sites .....Pohlia nutans
R. Endostome segments much more narrowly perforate, if at all; plant of very high alpine rock crevices .....Pohlia elongata

S. Leaves long-decurrent; exothecial cells almost isodiametric .....T
S. Leaves not or very little decurrent; exothecial cells longer than broad .....U

T. Plants pale, whitish-green; median cells 12-20 µm wide .....Pohlia wahlenbergii
T. Plants green to deep-green; leaves not or very little decurrent; median cells to 10 µm wide .....Pohlia ludwigii

U. Leaves serrulate to low serrate near the apices .....V
U. Leaves strongly serrate at apex .....Y

V. Plants of montane and coastal bogs; exothecial cells shorter; capsules 2-3:1, mostly pendant .....Pohlia sphagnicola not known from CA
V. Plants of alpine to subalpine sites; exothecial cells and capsules various .....W

W. Capsules almost erect, 2-3:1; median laminal cells 6-8:1; stems of plant reddened .....Pohlia erecta
W. Capsules inclined to pendent; median laminal cells short; stems green to red or brown .....X

X. Stems of plant green to brown; exothecial cells long-rectangular, more than 8:1; capsules mostly more than 4:1 ascending to horizontal .....Pohlia bolanderi
X. Stems of plant reddened; exothecial cells shorter; capsules 2-3:1, mostly pendent .....Pohlia vexans not known from CA

Y. Plant vigorous with the stems 5-25 mm high; cells of exothecium isodiametric; leaves spreading, with much enlarged perichaetial bracts .....Pohlia longibracteata
Y. Plant smaller, stems 3-8 mm high; cells of exothecium short-rectangular with the walls strongly sinuose; leaves erect or ascending and perichaetial bracts not so strongly enlarged .....Pohlia pacifica

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