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


Literature cited


Revised through 19 March 2007

Goals and Strategy

The goals of this Guide are to create an identification system for the intermediate level student that:

  • gives perspective on the characters used in the identification of mosses.  It uses the various character options that Mother Nature uses, rather than forcing everything into dichotomous states. The Guide therefore not only functions in a practical way to allow identification of genera, but also acts as a teaching tool to quickly train students as to which important characters are to be looked for.
  • gives perspective on the logical structure underlying the total system, i.e., the whole system is viewable in the Overview or on only two pages (Appendix B; Abbreviated Overview). If a user realizes that an error in identification has been made, then alternative routes are hopefully relatively apparent within the scheme.
  • sorts out the mosses into smaller Groups where each of the members included in a single Group is defined by one to three major characteristics. It minimizes the problems of a dichotomous key where a single wrong choice may not be discovered until the very end of the key; here a wrong choice usually involves “backing up” only to the start of a Group. The aim is to minimize the problem that “keys are made by those that don’t need them, for those that can’t use them."
  • is simple enough in internal structure to allow the user to correct, modify or customize it with relative ease. In particular, it can be downsized to smaller geographical or political regions by eliminating appropriate taxa.  An approximation of the geographical range for each genus is given in two different places within the Guide to facilitate downsizing and identification of genera. We welcome collaboration with any individuals that might be interested in downsizing the Guide for their particular area.  As "Regional" versions become available, they will be included in Appendix F. Two downsized versions are presently available: New England & New York, and the "MidWest".
  • allows modification without undue strain for use elsewhere in the world, particularly in the Northern Hemisphere. The Guide is in a ubiquitous format (msWord files) to allow customization of it by the maximal number of users.

To the maximum extent possible, the order in which characters are used adheres to the following guidelines:

  • obvious or unique characters will come first, and subtle, inconspicuous ones last. Characters visible to the naked eye will come first, followed sequentially by characters visible in the hand lens, then the dissecting microscope, and lastly by those only visible in the compound microscope. It must be emphasized, however, that there is variability in the amount of magnification required to see a given character, and thus some overlap exists between sections within the Overview.
  • characters relating to sexual condition (dioicous, synoicous, and etc.) and sporophytes are used only as a last resort in that they are often not available for many months of the year.
  • characters relating to habitat or substrate are used only as a last resort in that appropriate information is often not available at the bench, if suitable data were not recorded when the collections were made.

Parts to the Guide

Table of Contents



An outline of the identification system specifying the characters leading to corresponding Groups in which various genera will be found.

Full Sub-Guides

Three Sub-Guides (Initial, Freely branched & Rarely branched) allowing identification to a genus within a given Group.

Skeleton Sub-Guides (Skeletons)

Three Sub-Guides (Initial, Freely branched & Rarely branched) giving perspective on which genera possess species exhibiting the characters of a particular Group.


An alphabetical list of the genera to be found within the Guide giving perspective on: a) the number of species within a given genus; b) the approximate geographical distribution of that genus; and c) which Groups of the Guide contain that genus.

Geographical Abbreviations

Generalized abbreviations for particular areas; two-letter postal-code abbreviations for states and provinces within the United States and Canada.


Appendix A: Quick-Start Instructions.

Appendix B: Abbreviated Overview. Useful to those familiar with the system.

Appendix C: Glossary (In preparation).

Appendix D: Downloadable Files (Web version only).

Appendix E: Corrections and revisions.

Appendix F: Downsizing Recommendations & Regional Guides: For those who wish to downsize or use the Guide for a particular geographic area.

Other Appendices in preparation, but not yet ready for distribution, cover highly unique capsules, distinctive asexual brood bodies, and how to look at and find diagnostic features of mosses.


Genera Included & Nomenclature

The genera included, and the nomenclature for them, are found in the List of the Mosses of North America North of Mexico (Anderson, Crum & Buck, 1990). Updating the Guide will be necessary on completion of the Bryophyte Flora of North America project.


That found in the glossaries of most major floras and, as an optimum source, the beautifully illustrated Mosses & Other Bryophytes; an Illustrated Glossary (Malcolm & Malcolm, 2000).

Geographical Coverage & Distribution

North America north of Mexico; distributions are listed in the "full" Sub-Guides and the Concordance. Abbreviations follow the Concordance.

Order of use

This Guide is meant to be used sequentially as in other keys. A genus may be found only once in the Guide if an identifying character is extremely obvious, and it only has one such character. In most cases a given genus will be found in more than one Group based on the number of distinguishing characters it possesses in the "naked-eye", "hand-lens", or "dissecting microscope" categories. If, in the judgment of the authors, the genus can be identified with reasonable certainty without using "compound microscope" characters, then that genus will not be found in the latter Groups requiring that equipment.

If all of the species within a given genus do not posses a given character, indicated by a dagger (), then that genus will be found again later in the Guide in an appropriate Group.


(dagger): In part, i.e., not all of the species within a given genus, or the genus containing a species listed, will key to this Group. The other species in this genus will be found again later in the Guide in an appropriate Group.

+: More or less

Cell Ratios (length to breadth) ratios of medial, laminal leaf cells:

Freely branched (mostly pleurocarpous) mosses:

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:

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.

Number of stereid bands evident in costa cross-sections:

2* = costa with two stereid bands

1* = costa with one stereid band

0* = costa lacking stereid bands, i.e., +homogeneous

Cell surface ornamentation

 In the Overview and corresponding sections of the Full Sub-Guides, a distinction is made between "Cells distinctly papillose or prorulose" and "Cells indistinctly ornamented."  Distinct ornamentation, e.g., papillose, prorulose, mammillose or bulging, is, in our view, ornamentation that is higher and can be seen with reasonable confidence when observing leaves in surface view.  Indistinct ornamentation, on the other hand, is lower and requires that observations be made on the bends of folded leaves or leaf cross-sections.

Differences in treatment

There are some differences between the way the Freely branched and Rarely branched mosses are treated. Some of these differences may be removed in future versions; some will not.

  1. Species names are included in the Guide to Initial Groups (the Freely branched taxa ) and the Guide to Freely Branched Mosses when the genus is monotypic, or if the only possible choice at the end of a line is a single species.
  2. The leaf cell ratio definitions (long, intermediate, and short) differ slightly between the Freely branched and Rarely branched Guides.
  3. In the Skeleton Sub-Guide to Freely Branched Mosses, Groups P21 through P28 include all the freely branched moss genera. Those genera not in brackets require the criteria in Groups P21-P28 for successful identification. Those genera in brackets [--] should have been successfully identified in the preceding Groups. All genera are listed here as a reference to aid in overall perspective of the Freely branched mosses.

Note: Comments and suggestions regarding the Freely branched mosses should be directed to Diane Lucas; comments and suggestions regarding the Rarely branched mosses should be directed to Malcolm Sargent.


The files for this Guide have been created in Microsoft’s Word X for Mac. The page margins are generally 0.7” throughout, and the font is Times 11 except for headings and other unique situations. The files are continuously monitored for viruses, worms and etc. by Norton AntiVirus using the latest virus definitions.

When printing the msWord files from PC's or different operating systems, the page margins or page breaks may be slightly misaligned and require correction.  The PDF versions of the files do not normally have these alignment problems, or other Macintosh versus Windows incompatibilities.

The msWord and PDF files are also available from the authors via e.mail, or, if all else fails, on a CD.


Immature, sterile or small, and ratty specimens often cannot be identified with certainty.

While many genera can be identified in the field with relative certainty, some can only be identified if sporophytes are present, and others cannot be identified with certainty in the field under any circumstances.

Substrate specificity varies with conditions, i.e., with ideal conditions (often high humidity and moisture levels) taxa that might normally grow on bark may also be found on soil or rocks.

The characters used assume a “normal” level of hydration. Plants wet from a recent rain may look very different! For example, Hedwigia ciliata goes from being rigid and dull gray with tightly appressed leaves when dry, to soft and green with squarrose leaves when wet. Plants removed from their substrate may quickly alter their appearance. For example, leaves of Atrichum species will quickly fold up to the stem when the plants are removed from the soil.

The characters used assume a “typical” size. Plants growing under unusually adverse conditions, usually too dry, can be smaller than “typical”. Plants growing under unusually beneficial conditions, usually ideal moisture and humidity, can be larger than “typical”.

Color can vary for a variety of reasons. Most mosses darken in color as they mature and age. Many mosses growing under lower light intensities will be green (shade form), whereas they will be reddish or purplish (sun form) from various pigments when growing under higher light intensities.

Plants vary!” Lewis C. Anderson


The major sources of information for this Guide are: a): the Key to Moss Genera of North America North of Mexico (Vitt & Buck, 1992); b) the floras for eastern North America (Crum & Anderson, 1981), the Pacific Northwest (Lawton, 1971), and North America (Grout, 1931-1940); and c) the volume on the Pottiaceae by Zander (1993). Other sources occasionally providing highly relevant information included: a) the floras for Britain and Ireland (Smith, 1978), Japan (Noguchi, 1987-1994), Mexico (Sharp, Crum & Eckel 1994), and the West Indies (Buck, 1998); b) the increasing number of contributions to the Bryophyte Flora of North America on the Internet; and c) original articles in various bryological journals.

There has been a long history of efforts to make bryophyte identification easier for the non-specialist, and the works of Dunham (1916), Grout (1947), Bodenberg (1954), and Conard & Redfearn (1979) are good examples representing those efforts for North America. While the present Guide has benefited enormously from some ideas and concepts from these earlier works, the target audience is slightly different. This Guide is meant not for the absolute novice, but for the intermediate level naturalist or bryologist having difficulties with specialist keys.


This Guide is:

  • a work “in progress”, i.e., very much like open-source software, and in need of improvement and revision. We continue to discover ways to improve it as we work with actual collections, and constructive comments and criticisms would be greatly appreciated.  The authors are by no means experts on the moss flora of North America, and the preparation of this Guide has been, among other things, a learning experience meant to make the authors more familiar with the flora. Revisions and corrections will be posted in Appendix E of this website at appropriate intervals.
  • going to be "out of date" within the near future as the "Bryophyte Flora of North America" (BFNA) is completed. Our intention is to revise the Guide to make it agree with the BFNA as soon as the latter is complete.
  • meant for users with access to a hand-lens, a dissecting microscope, and, preferably, a compound microscope. It assumes that the user already has a basic understanding of the morphology and life cycle of mosses, and the terminology used to describe those items.
  • meant to be used with, and as an aid to, floras presently available whether they cover major areas of North America, specific regions, or individual states, i.e., it is not a "stand-alone" product. The floras have invaluable information including:
    1. full morphological descriptions of the mosses;
    2. habitat and substrate preferences;
    3. geographic ranges; and
    4. most importantly – illustrations.
  • totally artificial in that no effort is made to group phylogenetically related taxa.


The continuing stimulation, encouragement and advice on all things bryological from Barbara Andreas, Barbara Crandall-Stotler, Bill Buck, Bill McKnight, Dale Vitt, Janice Glime, Nancy Slack, Norton Miller, and Ray Stotler, among others, is most sincerely appreciated. Nancy Slack, in particular, has made noteworthy suggestions.

We are especially indebted to the Department of Plant Biology at the University of Illinois for generous financial support regarding design of the website, to E. Barbara Meyer for her expertise in designing the web version, and to Bill N. McKnight for extensive, detailed editorial suggestions.

Literature Cited

Anderson, L.E., H.A. Crum & W.R. Buck. 1990. List of Mosses of North America North of Mexico. The Bryologist 93:448-499.

Bodenberg, E.T. 1954. Mosses: A New Approach to the Identification of Common Species. Burgess Publishing Co., Minneapolis. 264 pp.

Buck, W.R. 1998. Pleurocarpous Mosses of the West Indies. Memoirs of the New York Botanical Garden, Vol. 82. The New York Botanical Garden Press, Bronx. 400 pp.

Conard, H.S. & P.L. Redfearn, Jr. 1979. How to Know the Mosses and Liverworts, 2nd Ed. Wm. C. Brown Co. Publishers, Dubuque. 302 pp.

Crum, H.A. & L.C. Anderson. 1981. Mosses of Eastern North America. Columbia University Press, New York.

Dunham, E.R. 1916. How to Know the Mosses. Houghton Mifflin Co., Boston. 287 pp.

Grout, A.J. 1931-1940. Moss Flora of North America North of Mexico, Volumes I-III. Published by the author, Newfane. 264, 285 & 275 pp.

Grout, A.J. 1947. Mosses with a Hand-Lens, 4th Ed. Published by the author, Newfane. 344 pp.

Lawton, E. 1971. Moss Flora of the Pacific Northwest. The Hattori Botanical Laboratory, Nichinan. 362 pp., 195 plates.

Malcolm, B. & N. Malcolm. 2000. Moss and Other Bryophytes; an Illustrated Glossary. Micro-Optics Press, Nelson, New Zealand. 220 pp.

Noguchi, A. 1987-1994. Illustrated Moss Flora of Japan, Parts 1-5. The Hattori Botanical Laboratory, Nichinan. 1,223 pp.

Norris, D.H. & J.R. Shevock. 2004. Contributions Toward a Bryoflora of California: 1. A Specimen-based Catalogue of Mosses. Madrono 51(1):1-131.

Sharp, A.J., H. Crum & P.M. Eckel. 1994. The Moss Flora of Mexico, Parts 1 & 2. The New York Botanical Garden, Bronx. 1,147 pp.

Smith, A.J.E. 1978. The Moss Flora of Britain and Ireland. Cambridge University Press, New York. 706 pp.

Vitt, D.H. & W.R. Buck. 1992. Key to the Moss Genera of North America North of Mexico. American Bryological & Lichenological Society, Madison. 29 pp.

Zander, R.H. 1993. Genera of the Pottiaceae: Mosses of Harsh Environments. Bulletin of the Buffalo Society of Natural Sciences, Vol. 32, Buffalo. 378 pp.

Photographic Credits

All photographs, except for the two Polytrichum photographs described below, were taken in recent years by Diane Lucas using a digital camera.

"Splash" page: Sweet Creek Falls, Lane Co., OR; SoBeFree Foray of March 2005.

Border for Introduction: Funaria hygrometrica.
Border for Overview: Sphagnum wulfianum.

Borders for Initials Groups: Sphagnum tenellum.
Borders for Freely branched mosses: Homalothecium spp.
Borders for Rarely branched mosses: Rhodobryum roseum.

Border for Concordance: Aulacomnium palustre.
Border for Geographical Abbreviations: Anomodon spp.

Banner for Appendix A: Sphagnum spp.
Border for Appendix B: Rhizomnium punctatum.
Banner for Appendix C: Polytrichum spp.
Banner for Appendix D: Dicranum fulvum
Banner for Appendix E: Fissidens spp.
Banner for Appendix F: Polytrichum spp.

Two Polytrichum photographs (banners for the Table of Contents and Appendix F) were taken by Malcolm Sargent in June of 1957 on the day that he first became sensitized to beauty in the Lilliputian world of bryophytes. The photographs were taken with a pre-WW II Exacta camera and Kodachrome film; the capsule close-up was taken with a 10" bellows attachment – the technology current at the time!

Parts to the Guide




Literature cited