World of Mosses website

A Graphic Guide to Ontario Mosses

by Robert Muma


Classification of Mosses


The  class MUSCI (Mosses) is divided into three sub-classes: (See illustrations)

1.  SPHAGNIDAE a small sub-class consisting of a single family and a single genus with 135 species worldwide.  These are the familiar SPHAGNUM mosses of the peat bogs.

2.  ANDREAEIDAE has two families; only two species in genus ANDREAEA are in our area.  These are boreal and alpine rock mosses.



3.  BRYIDAE contains all other mosses, of numerous genera and an estimated 10,000 species throughout the world.  They belong to many families, but it is more useful to divide the genera into two growth forms.  These are known as (a) Acrocarpous mosses and (b) Pleurocarpous mosses.  In any standard systematic guide to the mosses you will find (with only two or three exceptions) the first group in the first half of the book, and the second group in the latter half.  Recognition of these two growth forms constitutes the basis for this guide. (For moss-anatomy terms mentioned below, see Anatomy of a Typical Moss Plant.)  



Acrocarpous (a) Acrocarpous mosses are those which grow upright as individual plants, either separately or very close together to form a turf, tuft, or cushion.  In this group, the leaves nearly always have a costa, and the sporophyte grows from the tip or highest part (acros: highest; karpos: fruit).  Some of the common acrocarpous genera are DICRANUM, TORTELLA, BARBULA, MNIUM, BRYUM, POLYTRICHUM.  Perichaetial leaves not usually visible.  
Denoted by the vertical lines symbol
Pleurocarpous (b) Pleurocarpous mosses are the prostrate or creeping plants on ground, wood, or rock surfaces.  Some of these add new intertwining or overlaid growth each year to form mats.  The leaves are usually without costa and the sporophyte grows from the side of one of the branches of the plant (pleura: side; karpos: fruit).  The perichaetial leaves are longer and often quite different from the regular leaves.  Many of the pleurocarpous mosses are known popularly as "feather mosses" and "fern mosses", including the genera HYPNUM, THUIDIUM, AMBLYSTEGIUM, BRACHYTHECIUM, PLAGIOTHECIUM, HYLOCOMIUM.  
Denoted by the horizontal lines symbol



  • Note the symbols for acrocarpous  and pleurocarpous  moss forms and look for the clues to your specimen's genus under the applicable symbol in the Growth-Form plates.

  • If your specimen has sporophytes* check their posture on the Sporophyte Characteristics page.

  • Also check for Habitat.

Note:  In this Guide the name of each genus is shown in upper case letters, e.g. BRYUM.  Where a single species is relevant, the genus (in capitals) is followed by the specific name in lower case, as BRYUM argenteum.  Where broader classifications are mentioned, they are shown in upper case italics, i.e. family, order, sub-class, and the phylum (BRYOPHYTA).

  * Some mosses seldom produce sporophytes but tend to reproduce asexually.


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