A Perspective Oriented Guide for the Identification of North American Moss Genera
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Overview

Revised through 30 June 2010

Initial Groups ("naked-eye" characters)

Plants essentially leafless, consisting of strongly inclined, highly asymmetric capsules on stout papillose seta; the "bug-on-a-stick" mosses; WS *

Buxbaumia
Plants scattered on a bed of abundant, persistent protonemata; plants & leaves small to minute. Group A
Sub-Guide | Skeleton

Plants small to minute (mostly <5 mm high) with ±immersed capsules growing on bare soil, usually as winter annuals; the "pygmy ephemerals" as defined here.

Group B
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Plants rosulate (leaves in a tight rosette at stem apex) and large (diameter 1-2 cm); WS Rhodobryum
Plants erect with clusters of branches (fascicles) along the stem & at the apex (capitulum); WS Sphagnum

In part, i.e., not all of the species within this genus will key to this Group. The other species will key to an appropriate Group.

Plants from an erect, unbranched stipe, and either dendroid (tree-like) or frondose (fern-like).# Group C
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# Note - the several mostly prostrate "fern-mosses" lacking a stipe are NOT included here, but will be found in the pleurocarpous Groups below.

Plants with pendulous branches hanging loosely from tree branches. Group D
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Plants projecting horizontally from vertical surfaces or with upturned/curled branch tips. Group E
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Plants growing on dung, decaying animal matter, or other highly nitrogenous materials; the "dung mosses". Group F
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Plants lacking any of the above unique “growth forms”; Continued below at left margin.

Plants freely branched, i.e., with leafy stems & branches; usually prostrate in wefts or mats.
Mostly pleurocarpous or cladocarpous mosses, but also including an occasional acrocarpous moss, e.g., Plagiobryum,
Racomitrium, Schlotheimia & etc.

Groups P1 on

Plants rarely branched, i.e., lacking obvious branching; usually erect in tufts, cushions or turfs.
Mostly acrocarpous mosses, but also including an occasional pleurocarpous or cladocarpous moss, e.g., Hedwigia.

Groups A1 on

Freely Branched (mostly pleurocarpous) Mosses

Plant Characters Section (naked eye)

Plants strongly flattened (complanate) or angular. Group P1
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Plants julaceous both wet & dry (shoots round; leaves crowded, overlapping, and appressed).# Group P2
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Leaves spreading at right angles (squarrose) or squarrose-recurved; leaf tips often channeled. Group P3
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Plants with erect branches from a creeping stem. Group P4
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Plants with leaves sickle-shaped and turned to one side (falcate-secund). Group P5
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Plants or leaves lacking any of the above unique characters; Continued below at left margin.

# Note - many other taxa have leaves crowded & appressed when dry, but spreading when wet.


Leaf and Stem Characters Section (hand lens)

Plants with paraphyllia or tomentum on stems. Group P6
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Plants with red stems. Group P7
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Plants appearing “braided” (shoots flat on top & bilaterally symmetric; leaves falcate-secund). Group P8
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Leaves undulate or rugose (irregular undulations). Group P9
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Leaves dimorphic (2 different forms [size and/or shape] on the same axis).# Group P10
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Leaves with awns or hair points. Group P11
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Plants thread-like (stems little branched; leaves <1 mm). Group P12
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Plants or leaves lacking any of the above unique characters; Continued below at left margin.

# Note - many other taxa have stem leaves differing from branch leaves.


Costa Characters Section (dissecting scope)

Costa double & more than 1/3 leaf length. Group P13
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Costa single & narrow.

Leaves with distinct decurrencies.

Group P14
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Leaves with a distinct marginal border.

Group P15
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Leaves with distinct alar cells.

Group P16
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Costa short & double, or none.

Leaves with distinct decurrencies.

Group P17
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Leaves with a distinct marginal border.

Group P18
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Leaves with distinct alar cells.

Group P19
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Costa of uncommon or variable form (Y-shaped; forked; with lateral spurs or supplementary costae) Group P20
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Costa neither double & long, nor of an uncommon form; leaves lacking any of the above unique characters; Continued below at left margin.

Reminder - Definitions for cell length to breadth ratios are found in the Introduction, the Overview & at the end of this section.

Leaf Cell Ratio Section (compound microscope)

Leaf cells long (>8:1).

Cells distinctly papillose or prorulose.

Group P21
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Cells smooth or indistinctly ornamented.#

Costa single.

Group P22
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Costa double (long or short), or none.

Group P23
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Leaf cells intermediate (3-8:1).

Cells distinctly papillose or prorulose.

Group P24
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Cells smooth or indistinctly ornamented.#

Costa single (narrow or wide).

Group P25
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Costa double (long or short), or none.

Group P26
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Leaf cells short (<3:1).

Cells distinctly papillose or prorulose.

Group P27
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Cells smooth or indistinctly ornamented.#

Group P28
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# Note - cells indistinctly papillose, i.e., low papillae or projections. An expanded explanation of the difference between "Distinct" and "Indistinct" surface ornamentation is found in the Introduction.


Cells = medial, laminal cells; cells ~2/3 of the way from insertion to apex, midway between the costa & the margin.

Cell length to breadth ratio:

Long cells: >8:1; commonly termed linear, or linear-flexuose.

Intermediate cells: 3-8:1; commonly termed elongated, oblong-rhomboidal, fusiform, or elliptical.

Short cells: <3:1; commonly termed isodiametric, quadrate, rounded-quadrate, or rhombic.

Rarely Branched (mostly acrocarpous) Mosses

"Naked-eye" Characters

Shoots flattened or angular (2-5 ranked) in cross-section, i.e., not round. Group A1
Sub-Guide | Skeleton
Shoots julaceous both wet and dry (catkin-like; leaves crowded, overlapping and appressed).# Group A2
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Stems tomentose (densely covered by rhizoidal tomentum to near the apex). Group A3
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Stems red. Group A4
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Leaves squarrose-recurved (spreading at right angles with down-turned tips; shoots brush-like). Group A5
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Leaves falcate-secund (sickle-shaped & turned to one side; shoots broom-like). Group A6
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Leaves subulate-setaceous (awl, bristle, or needle-like; length to breadth 8:1 or greater). Group A7
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Shoots, stems or leaves lacking any of the above unique characters; Continued below at left margin.

# Note - many species have leaves crowded and appressed when dry, but spreading when wet.


"Hand-lens" Characters

Leaves finger-like and irregularly inserted; NW. Takakia
Leaves dimorphic (2 different forms [size and/or shape] on the same axis). Group A8
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Leaves with a distinct hyaline hair-point or awn on vegetative leaves.# Group A9
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Leaves with lamellae, ridges, or filaments on their laminae or costae. Group A10
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Leaves undulate (distinct transverse waves or ridges). Group A11
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Leaves involute (margins distinctly incurved, inrolled, spirally inrolled or inflexed). Group A12
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Leaves lacking any of the above unique characters; Continued below at left margin.

# Note - some species have these hair-points only on the upper leaves; species with hair-point son perichaetial leaves only will be found in other Groups.


"Dissecting microscope" Characters

Leaves +all costa, lacking laminae; multistratose. Group A13
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Leaves with a broad, single costa (>1/3 the leaf width). Group A14
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Leaves with a narrow, single costa.

Leaves with bases distinctly incurved to expanded & sheathing.

Group A15
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Leaves with long, pronounced decurrencies.

Group A16
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Leaves with a defined group of hyaline cells that stand in distinct contrast to densely papillose or chlorophyllose cells

Group A17
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Leaves with distinct marginal border of differentiated cells (ciliate; cells long, short, pale, hyaline, or thick-walled)

Group A18
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Leaves with distinctly differentiated alar cells (cells enlarged, inflated, quadrate, thick-walled, or colored)

Group A19
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Leaves with costae extremely reduced to lacking. Group A20
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Leaves lacking any of the above unique characters; Continued below at left margin.

Reminder - Definitions for cell length to breadth ratios are found in the Introduction, the Overview & at the end of this section.

"Compound microscope" Characters

Leaf cells long (>5:1).

Cells smooth.

Group A21
Sub-Guide | Skeleton
Leaf cells intermediate in length (2-5:1).

Cells distinctly papillose.

Group A22
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Cells distinctly prorulose.

Group A23
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Cells smooth or indistinctly ornamented.#

GroupA24
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Leaf cells short (<2:1).

Cells distinctly papillose.

Group A25
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Cells smooth or indistinctly ornamented.#

Group A26
Sub-Guide | Skeleton

# Note - cells bulging, mammillose (both bulging and papillose) or indistinctly papillose, i.e., low papillae. An expanded explanation of the difference between "Distinct" and "Indistinct" surface ornamentation is found in the Introduction.


Cells = medial, laminal cells; cells ~2/3 of the way from insertion to apex, midway between the costa and the margin.

Cell length to breadth ratio:

Long cells: >5:1; commonly termed linear.

Intermediate cells: 2-5:1; commonly termed elongated, rectangular, hexagonal, or rhomboidal.

Short cells: <2:1; commonly termed isodiametric, quadrate, rounded-quadrate, or sub-quadrate.

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