Bryum Hedwig, 1801.

Bryum argenteum, photo by Wilson of Coleman 772

Bryum may well be the largest genus of mosses in the world with over a thousand described species, but it has been split into segregate genera by Spence (2005). It is exceptionally well represented in temperate and polar regions, and is especially common and diverse in California. The cells are mostly less than 4:1, and this differentiates local species of Bryum from Pohlia and its kin. The Bryaceae have recently undergone significant realignment, partly based on DNA studies. Many genera, historically placed in the Bryaceae, such as Pohlia, Epipterygium and Roellia, are now placed in the Mniaceae. Leptobryum has been transferred to the Meesiaceae.

Key to Bryum Etc.

Mosses included in this section are costate and acrocarpous mosses mostly with papillose rhizoids and with rather large (more than 12 µm broad) hexagonal to rectangular, rather thin-walled cells. The pendant to horizontal capsules are mostly long cylindric and the peristome is complete or nearly so. The cells are short, seldom more than 4:1, and the costa has only an abaxial stereid band or none at all.

Species included in this key are in Bryaceae, except Roellia (Mniaceae):
Brachymenium exile (Dozy & Molkenboer) Bosch & Sande Lacoste, not known from CA
Brachymenium systylium (C. Müller Hal.) A. Jaeger, not known from CA
Brachymenium spirifolium (C. Müller Hal.) A. Jaeger, not known from CA
Bryum algovicum Sendtner in C. Müller Hal.
Bryum alpinum Hudson ex Withering
Bryum amblyodon C. Müller Hal.
Bryum arcticum (R. Brown) Bruch & W. P. Schimper, not known from CA
Bryum argenteum Hedwig
Bryum badium (Bridel) W. P. Schimper
Bryum barnesii Wood in W. P. Schimper
Bryum bicolor Dickson
Bryum bimum (Schreber) Turner
Bryum blindii Bruch & W. P. Schimper
Bryum caespiticium Hedwig
Gemmabryum californicum, recognized from CA since 2004
Bryum calobryoides Spence
Bryum canariense Bridel
Bryum capillare Hedwig
Bryum chryseum Mitt., recognized from CA since 2004
Bryum cyclophyllum (Schwägrichen) Bruch & W. P. Schimper
Bryum elegans Nees in Bridel
Bryum erythroloma (Kindberg) Syed
Bryum flaccidum Bridel
Bryum gemmascens Kindberg
Bryum gemmiferum R. Wilczek & Demaret
Bryum gemmilucens R. Wilczek & Demaret
Bryum gemmiparum De Notaris
Bryum klinggraeffii W. P. Schimper, not known from CA
Bryum knowltonii Barnes, not known from CA
Bryum laevifilum Syed
Bryum lanatum (Palisot de Beauvois) Bridel
Bryum lisae De Notaris
Bryum meesioides Kindberg in Macoun
Bryum microerythrocarpum C. Müller Hal. & Kindberg
Bryum miniatum Lesquereux
Bryum muehlenbeckii Bruch & W. P. Schimper
Bryum pallens Swartz
Bryum pallescens Schleicher ex Schwägrichen
Bryum pseudotriquetrum (Hedwig) Gaertner, Meyer & Scherbius
Bryum pyriferum Crundwell & Whitehouse
Bryum radiculosum Bridel
Bryum rubens Mitten
Bryum schleicheri Schwägrichen, not known from CA
Bryum subapiculatum Hampe
Bryum tenuisetum Limpricht
Bryum torquescens Bruch
Bryum turbinatum (Hedwig) Turner
Bryum uliginosum (Bridel) Bruch & W. P. Schimper
Bryum violaceum Crundwell & Nyholm
Bryum weigelii Sprengel
Plagiobryum zierii (Hedwig) Lindberg, not known from CA
Roellia roellii (Brotherus ex Röll) Andrews ex H. Crum

Outside of the family Bryaceae, gametophytes of Bryum may most easily be confused with members of the Splachnaceae (a family not yet documented for California) and Funariaceae. Members of the former family are usually collected with sporophytes, and the long or broad hypophysis characteristic of that family should allow easy differentiation. Similarly, the Funariaceae usually are collected with sporophytes, and can be recognized by the presence of a dome-shaped operculum that has essentially no apiculus. The basic pattern of areolation of the leaves of the Bryaceae typically can be distinguished from that of the Funariaceae and the Splachnaceae. The cells of the Bryaceae vary around a rhomboidal pattern; the cells of the Splachnaceae and Funariaceae vary around a quadrate to rectangular pattern. This results in a pattern of straight rows of cells in the latter two families. The leaves of the Splachnaceae and Funariaceae are mostly broadest above the middle; those of the Bryaceae are usually broader below the middle. The Bryaceae have axillary hairs of almost equal diameter from base to apex; the Funariaceae and the Splachnaceae usually have the apical cells of greater diameter than the basal cells. Finally, there is a tendency in the Bryaceae for the leaf buttress cells to extend as a shelf-like structure after leaf excision; the Splachnaceae and Funariaceae have no such shelf-like structure after leaf excision.

Features of Bryum that allow identification to species include patterns of asexual reproduction. Some species of Bryum have multicellular, mostly spherical gemmae (tubers) of specific colors shallowly buried under the substratum near the stem base. Other species of Bryum have multicellular, usually elliptical or filamentous, stalked structures in upper leaf axils. The coloration of the leaf base may be reddened or it may be concolorous with the rest of the leaf. Such coloration features are features of the actual leaf lamina but coloration simply of the costa base is mostly irrelevant to species distinction. All Bryum have somewhat narrowed cells at the immediate border. The strength of the leaf border is important in species distinction. All Bryum have somewhat narrowed cells at immediate border but some species have markedly more elongate and narrow cells in several parallel series, and these cells of the limbidium may even make a multistratose border.

Spence (1988) presented a very usable key to western North American species of Bryum, and much of the key that follows is heavily indebted to Spence. Since the writing of our key, Spence has produced a highly innovative treatment in FLORA OF NORTH AMERICA; we suggest it be used directly.

A. Median leaf cells at least in part more than 50 µm broad; margin strongly differentiated .....Roellia: R. roellii
A. Median leaf cells more narrow .....B

B. Leaf cells echlorophyllose in distal 1/2, the leafy plant thus appearing silvery to whitish; plant of ruderal habitats, or on thin soil over rocks .....C
B. Leaves and plant not so whitish .....E

C. Costa excurrent; plant of thin soil in frequently drying sites .....Bryum lanatum
C. Costa percurrent to subpercurrent; plant of various sites, often ruderal .....D

D. Plants with a reddish blush on the older portions of the stems; neck of capsule as long as urn; plant of thin soil in deep recesses of rock outcrops in alpine and subalpine areas .....Plagiobryum: P. zierii not known from CA
D. Plants whitish or greenish to base; neck of capsule short; plant of disturbed soil and cracks in rocks, sometimes on highly nitrogenous soil such as that below bird roosts .....Bryum argenteum

E. Leaves with a strong limbidium that is bistratose at least in the basal 1/3 .....F
E. Leaves with limbidium strong to weak or absent, consistently unistratose .....M

F. Leaves almost orbicular but so strongly distorted when dry as to obscure that character; leaf apex bluntly obtuse with costa ending before the apex .....Bryum cyclophyllum
F. Leaves ovate to lanceolate with acute apices; costa mostly percurrent to excurrent .....G

G. Leaves ovate to ovate-lanceolate, decurrent with the decurrency extending to the insertion of the next leaf; distal leaf margin minutely serrulate to entire .....Bryum weigelii
G. Leaves not so strongly decurrent .....H

H. Most median leaf cells 25-40 µm wide; leaves broadest near middle, about 2.5:1, not contorted when dry; plants mostly with a pinkish wash; peristome with cilia fully developed; .....Bryum schleicheri not known from CA
H. Most median leaf cells less than 30 µm wide; leaf shape various but mostly more narrow, at least somewhat contorted when dry; plants variously colored; peristome with cilia absent or present .....I

I. Leaves about 2.5:1; leaf margins plane throughout; capsules turbinate, less than 2:1 .....Bryum turbinatum
I. Leaves mostly 3:1 or greater; margins recurved at least near base; capsules more elongate .....J

J. Cells of leaf base not reddened; costae not reddened in 10% KOH; plant synoicous .....Bryum arcticum not known from CA
J. Cells of leaf base away from the costa reddened; costa and stem very deeply reddened in KOH; plant not synoicous .....K

K. Peristome with cilia reduced or absent; spores mostly more than 25 µm in diameter .....Bryum uliginosum
K. Peristome with cilia fully developed; spores mostly less than 25 µm in diameter .....L

L. Some capsules in excess of 5 mm long, somewhat curved at the well-defined neck; median exothecial cells elongate, 3-4:1; spores 14-20 µm in diameter .....Bryum meesioides
L. Capsules mostly about 3 mm long; median exothecial cells quadrate to short rectangular; spores 20-30 µm in diameter .....Bryum pallens

M. Leafy stems with concave leaves closely overlapping without significant reflexing of apices, thus with an overall julaceous appearance .....N
M. Leafy stems not julaceous .....P

N. Stem heavily fluted in cross-section; leaves longer than 2 mm, heavily reddened throughout; cells of leaf base somewhat inflated .....Bryum miniatum
N. Stem not fluted in cross-section; leaves smaller, typically reddened only near base; cells on leaf base not inflated .....O

O. Cells of distal lamina 2-3:1, leaf apices broadly acute on distal portions of the very short stem but almost truncate or cucullate on lower portions of stem .....Bryum calobryoides
O. Cells of distal lamina mostly more than 4:1; leaf apices acute to acuminate, not at all cucullate .....Bryum blindii

P. Basal leaf cells quadrate or nearly so across the width of the leaves, obviously set off from the hexagonal to rhomboidal cells of the median and distal portions of the leaf .....Q
P. Basal leaf cells rectangular with parallel walls, gradually transitting to the hexagonal to rhomboidal cells of the median and distal portions of the leaf .....AG

Q. Rhizoids deep red-brown, sparingly papillose to almost smooth, arising from a line of nematogons arranged in a single row along abaxial line of leaf insertion .....Brachymenium: B. systylium not known from CA
Q. Rhizoids of various colors, strongly papillose with nematogons not arranged in a single transverse row on stem .....R

R. Costa not reaching leaf apex; leaves broadly ovate and deeply concave without a well-defined limbidium; clones easily fragmented into the constituent individual axes .....Bryum gemmascens
R. Plants not in all respects as above .....S

S. Plants mostly more than 1 cm high with leaves somewhat contorted distally; leaves with margins somewhat recurved .....T
S. Plants smaller with leaves closely imbricate, not contorted .....U

T. Leaves with a strong reddish coloration .....Bryum muehlenbeckii
T. Leaves green .....Bryum gemmiparum

U. Bulbils present in upper leaf axils, becoming visible by their growth that causes leaf spreading; costa percurrent; stems mostly less than 1 cm long .....V
U. Bulbils not in leaf axils but with rhizoidal tubers functioning in asexual reproduction .....Z

V. Plants with a brownish to reddish-brown spinose awn at least on the distal portions of the leaves .....Brachymenium: B. exile not known from CA
V. Plants with awn concolorous with rest of leaf or with the costa not excurrent .....W

W. Bulbils mostly 1-2 per upper leaf axil, usually with leaf primordia well developed, several cells wide at base .....Bryum bicolor
W. Bulbils 2-5 per upper leaf axil .....X

X. Bulbils small, 100-200 µm in diameter; primordia absent or difficult to define .....Bryum gemmilucens
X. Bulbils larger, with obvious leaf primordia on their distal portions .....Y

Y. Bulbils with leaf primordia blunt to broadly acute at apices, mostly more than 250 µm in diameter .....Bryum barnesii
Y. Bulbils with leaf primordia narrow and needle like, mostly less than 250 µm in diameter .....Bryum gemmiferum

Z. Rhizoidal tubers red to red-brown with individual cells strongly protuberant or mammillose bulging .....AA
Z. Rhizoidal tubers variously colored, smooth on surface with individual cells not bulging .....AB

AA. Limbidium well-defined at mid-leaf; rhizoidal tubers mostly more than 125 µm in diameter .....Bryum rubens
AA. Limbidium absent or inconspicuous; rhizoidal tubers mostly less than 100 µm in diameter .....Bryum klinggraeffii not known from CA

AB. Rhizoidal tubers brown .....AC
AB. Rhizoidal tubers red to yellow .....AD

AC. Rhizoidal tubers mostly not spherical, often pyriform, to 75 µm in longest diameter .....Bryum pyriferum
AC. Rhizoidal tubers spherical, more than 125 µm in diameter; costa long excurrent .....Bryum radiculosum

AD. Rhizoidal tubers produced on violet rhizoids .....Bryum violaceum
AD. Rhizoidal tubers produced on brownish rhizoids .....AE

AE. Rhizoidal tubers yellow, less than 100 µm in diameter .....Bryum tenuisetum
AE. Rhizoidal tubers red to yellow, larger .....AF

AF. Many of the internal basal cells of the leaf short rectangular; rhizoidal tubers yellow or with a yellowish blush .....Bryum subapiculatum
AF. Basal cells of the leaf consistently quadrate; rhizoidal tubers reddish .....Bryum microerythrocarpum

AG. Leaves broadest above or at the middle and thus appearing obovate .....AH
AG. Leaves broadest near the base .....AP

AH. Plants with filiform gemmae present in upper leaf axils .....AI
AH. Plants without such filiform gemmae .....AJ

AI. Leaves decurrent with limbidium reaching nearly or completely to the leaf apex; costa percurrent to short excurrent; gemmae long and mostly unbranched, strictly axillary in insertion .....Bryum flaccidum
AI. Leaves not decurrent with limbidium mostly very weak or absent at leaf apex; costa weak, mostly ceasing before leaf apex; gemmae extensively branched, inserted in leaf axils and on leaf base .....Bryum laevifilum

AJ. Leaves evenly spaced, not rosulate, somewhat glaucous, laterally twisted when dry .....AK
AJ. Leaves rosulate on stems, green, erect or clockwise twisted around stem when dry .....AL

AK. Leaf lamina orbicular to broadly ovate; limbidium confluent with costa at apex; plant glaucous .....Bryum elegans
AK. Leaf lamina elliptical, 2.5-3.5:1; limbidium ending before leaf apex; plant glossy .....Brachymenium: B. spirifolium not known from CA

AL. Rosulate comas forming interrupted tufts; costa short excurrent with awn reflexed back from plane of leaf; limbidium poorly defined above the leaf middle .....Bryum canariense
AL. Stems usually with only a single rosulate cluster; excurrent costa not reflexed; limbidium various .....AM

AM. Leaves distinctly decurrent, mostly washed with red even distally; costa percurrent to short excurrent .....Bryum erythroloma
AM. Leaves not decurrent, reddened only near base; costa various .....AN

AN. Limbidium weak or absent above; margins near apex nearly entire; innovational branchlets below perichaetia with leaves broader and shorter, nearly imbricate .....Bryum gemmascens
AN. Limbidium strong even near leaf apex; margins near apex serrulate to serrate; innovational branchlets with leaves similar to leaves of main branches .....AO

AO. Plant synoicous or autoicous; leaves erect but contorted when dry; capsule with reddish coloration when mature .....Bryum torquescens
AO. Plant dioicous; leaves clockwise twisted around stem when dry; capsule mostly brown when mature .....Bryum capillare

AP. Leaves without a defined limbidium; costa subpercurrent, percurrent or only minutely excurrent .....AQ
AP. Leaves with limbidium obvious to near apex; costa evidently excurrent .....AR

AQ. Median leaf cells short hexagonal, more than 20 µm broad; leaf apex obtuse with costa mostly ceasing below apex .....Bryum muehlenbeckii
AQ. Median leaf cells linear, more than 6:1, less than 10 µm broad; leaf apex acute with costa ending at apex .....Bryum alpinum

AR. Leaves comosely arranged at stem apices; capsule mostly less than 2.5:1; limbidium broad with at least 5 rows of cells at leaf apex .....AS
AR. Leaves equidistantly arranged along stem; capsule mostly longer; limbidium present throughout but more narrow .....AU

AS. Leaves distally narrowly acute, gradually contracted to an excurrent costa that exceeds 0.5 mm in length .....AT
AS. Leaves with costa shorter and with the lamina not so gradually contracted .....Bryum knowltonii not known from CA

AT. Endostome and exostome fused with space between the two rows of teeth forming small chambers; capsule red .....Bryum algovicum
AT. Endostome and exostome not so fused; capsule yellow to orange .....Bryum amblyodon

AU. Leaves narrowly decurrent but with decurrency reaching nearly to base of next leaf; basal cells thick-walled with lumen:wall ratio about 4-6:1, and with these cell walls irregularly thickened to pitted .....AV
AU. Leaves not so strongly decurrent; basal cells not so strongly thick-walled, never pitted .....AW

AV. Plant synoicous .....Bryum bimum
AV. Plant dioicous .....Bryum pseudotriquetrum

AW. Leaf cells seldom more than 2.5-3:1, broadly hexagonal; limbidium broader .....AX
AW. Upper leaf cells on distal leaves at least in part long rhomboidal, 5-6:1; limbidium only 2-3 cells wide near leaf apex .....AY

AX. Endostome processes with perforations as broad as long; spores 12-16 µm in diameter .....Bryum lisae
AX. Endostome processes with perforations to twice as broad as long; spores 18-20 µm in diameter .....Bryum pallescens

AY. Leaves with spinose awn that is more than 1/2 as long as the leaf lamina .....Bryum badium
AY. Leaves with nearly smooth awn that is less than 1/2 as long as the leaf lamina .....Bryum caespiticium