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The character categories and their possible forms are:

Western bryophytes
My Lord's Throat

The wonderfully-named glen "My Lord's Throat", east of Alford, Aberdeenshire, has a surprisingly western bryophyte flora for a location on the east of Scotland.

Granite boulders are strewn over the steep slopes in this birch woodland, providing a niche for species favouring acid rocks. The photo shows a rich-green mound of Polytrichum accompanied by paler cushions of Bryum.

When a leaf is not a leaf
The green moss plant is not a diminutive, reduced version of a flowering plant

Bryophyte "organs and tissues" may resemble those of vascular plants, but they must have evolved separately and are not homologous morphological structures. To see why this is so, you have to remember that the leafy moss plant, the gametophyte, comprises haploid cells. Cells of this ploidy in flowering plants are found in the pollen grains and the ovules, while the leafy shoots are part of the diploid sporophyte plant body. The sporophyte on mosses comprises the semi-parasitic seta and moss capsule.

And so although we use terms such as shoot and leaf to describe parts of mosses that play similar roles to the same-named parts in vascular plants, they arise in a different generation in the life cycle. If a pollen grain or ovule developed photosynthetic shoots and leaves, we'd have something more akin to the moss gametophyte.

The overall similarity in plant structure between moss gametophytes and vascular plant sporophytes must be the result of convergent evolution.

To reflect these different origins, technical terms for the shoot-like and leaf-like parts of mosses have been defined, although these are rarely used by bryologists. However, this distinct nature of moss parts is worth bearing in mind and may go some way to explaining the ways in which moss "shoots" and "leaves" can demonstrate innovations in form and structure that are not found in vascular plants.

Corrie of Balglass
Cloch Burn

Cloch Burn drops over the cliffs at the Corrie of Balglass near Fintry, Stirlingshire, creating a variety of niches inhabited by a range of mosses and liverworts.

Bryophyte books
More content
There's more content to come on this page in particular, as moss leaves have many structures helpful in species determination. Coming soon are species lists grouped according to the characters listed below.
    Leaf margins:
  • Recurved
  • Not recurved
    Leaf surface:
  • Wavy / undulate
  • Flat / Smoothly curved
  • Distinctly folded or with a keel
    Outline shape of the leaves
    Colour of the leaves:
  • Yellow-green
  • Yellow
  • Orange
  • Red
  • Red-brown
  • Black
  • Silvery
    Shape of the leaf cells in different parts of the leaf
Hairpoint present
  • Bryum capillare
  • Bartramia pomiformis
  • Brachythecium albicans
  • Grimmia laevigata
  • Hedwigia stellata
  • Orthotrichum diaphanum
  • Pogonatum aloides Note:
    The marginal border cells in Pogonatum aloides continue into a robust "spine" at the tip of the leaves.
  • Polytrichum commune Note:
    Polytrichum commune has toothed or jagged points at the ends of the leaves.
  • Polytrichum piliferum Note:
    Polytrichum piliferum has toothed or jagged points at the ends of the leaves.
  • Racomitrium heterostichum
  • Racomitrium lanuginosum
  • Syntrichia laevipila
  • Syntrichia ruralis
  • Tetraplodon mnioides Note:
    The long drawn-out wavy leaf point in Tetraplodon mnioides may have small teeth.
  • Tortula muralis
Syntrichia ruralis ssp. ruraliformis Syntrichia ruralis ssp. ruraliformis (Pottiaceae)


Syntrichia ruralis ssp. ruraliformis

Hairpoint present

Syntrichia ruralis ssp. ruraliformis has very conspicuous hairpoints, as do many of the Syntrichiums. Note the rough edges on the hairpoint margins, almost like teeth.

Hairpoints vary in their length relative to the leaf, some just projecting slightly from the leaf apex while others can be longer than the leaf "blade" iteself.

As hairpoints are generally unpigmented, they perhaps help reduce water loss by the leaves through reducing air flow over the leaf surfaces, while not interfering with light penetration to the photosynthetic cells of the moss.


No hairpoint
  • Atrichum undulatum
  • Amblystegium serpens
  • Andreaea
  • Aulacomnium androgynum
  • Aulacomnium palustre
  • Barbula sardoa
  • Barbula unguiculata
  • Brachythecium populeum
  • Brachythecium rutabulum
  • Bryum alpinum
  • Bryum argenteum
  • Bryum pallens
  • Bryum pseudotriquetrum
  • Calliergonella cuspidata
  • Ceratodon purpureus
  • Cratoneuron filicinum
  • Ctenidium molluscum
  • Dicranoweisia cirrata
  • Eurhynchium striatum
  • Calliergon giganteum
  • Climacium dendroides
  • Fissidens bryoides
  • Funaria hygrometrica
  • Gymnostomum aeruginosum
  • Gyroweisia tenuis
  • Homalothecium sericeum
  • Hylocomium splendens
  • Hypnum cupressiforme
  • Hypnum jutlandicum
  • Kindbergia praelonga
  • Leucodon sciuroides
  • Mnium hornum
  • Orthotrichum cupulatum
  • Orthotrichum rivulare
  • Orthotrichum stramineum
  • Palustriella commutata
Homalothecium sericeum Homalothecium sericeum (Brachytheciaceae)


Fissidens taxifolius

Hairpoint absent

It's not very easy to show a photograph of a character that does not exist! The example of a moss with no hairpoint I've chosen here, Homalothecium sericeum, has interesting longitudinal folds on the leaves.

  • Philonotis fontana
  • Plagiomnium ellipticum*
  • Plagiothecium undulatum
  • Pleurozium schreberi
  • Pohlia melanodon
  • Pohlia wahlenbergia
  • Pseudocrossidium revolutum
  • Pseudoscleropodium purum
  • Pterygonium gracile
  • Racomitrium fasciculare
  • Rhynchostegium confertum
  • Rhytidiadelphus loreus
  • Rhytidiadelphus triquetris
  • Rhizomnium punctatum
  • Schistidium rivulare
  • Thamnobryum alopecurum
  • Tortella tortuosa
  • Trichostomum brachydontium
  • Ulota bruchii
  • Ulota phyllantha
  • Warnstorfia fluitans
Hairpoints are important, and much discussed, diagnostic characters, particularly regarding their length relative to the length of the leaf. I was therefore surprised at the length of the list here, comprising numerous common UK moss species, all with no hairpoint.

I've not yet attempted to see if there's any correlation between presence / absence of hairpoints and the nature of the niches inhabited by each group of mosses.


Recurved, hooked, squarrose
  • Ctenidium molluscum
  • Palustriella commutata
  • Rhytidiadelphus squarrosus
Palustriella commutata Palustriella commutata (Amblystegiaceae)
Palustriella commutata

Recurved leaves

The illustrated moss is Palustriella commutata whose leaves are described as circinate-secund, i.e. curved and arising from one side of each shoot.

I've combined a range of features in this single character, as there appears to be few species that show these leaf forms. The essential feature highlighted is that the leaves are bent along their long axis in one way or another.

It seems reasonable to assume that any degree of folding of moss leaves will tend to help retain moist air, but at the expense of not presenting as much of the leaf surface perpendicular to the rays of the sun, compared to what properly-oriented flat leaves can achieve.


Excurrent nerve
  • Bryum capillare
  • Fissidens bryoides
  • Funaria hygrometrica
  • Plagiomnium ellipticum*
  • Syntrichia laevipila
  • Syntrichia ruralis
  • Tortula muralis
Syntrichia laevipila Syntrichia laevipila (Pottiaceae)
Syntrichia laevipila

Excurrent costa

Species in the genus Syntrichia make a good subject for comparing variations in costa length relative to the leaf. In S. laevipila the costa clearly projects beyond the rounded leaf tip.

The example shown here of a moss with an excurrent costa, illustrates the character very clearly. It can be seen that the costa is devoid of pigmentation after it leaves the leaf "blade", becoming a hyaline hairpoint.

The costa is associated with structural rigidity and perhaps some degree of water transport, but after it transitions into a hairpoint, it's role may be primarily to reduce water loss.


Percurrent nerve
  • Atrichum undulatum
  • Aulacomnium androgynum
  • Aulacomnium palustre
  • Barbula sardoa
  • Barbula unguiculata
  • Brachythecium rutabulum
  • Bryum alpinum
  • Bryum pallens
  • Bryum pseudotriquetrum
  • Ceratodon purpureus
  • Climacium dendroides
  • Dichodontium palustre
  • Dicranoweisia cirrata
  • Fissidens dubius
  • Philonotis fontana
  • Pogonatum aloides
  • Polytrichum commune
  • Polytrichum piliferum
  • Orthotrichum rivulare
  • Orthotrichum stramineum
  • Palustriella commutata
  • Plagiomnium ellipticum*
  • Pseudocrossidium revolutum
Rhizomnium punctatum Rhizomnium punctatum (Mniaceae)


Rhizomnium punctatum

Percurrent costa

The large broad leaves of the moss Rhizomnium punctatum have a conspicuous costa, making it easy to see how far it progresses along the length of the leaf.

  • Racomitrium fasciculare
  • Rhizomnium punctatum
  • Schistidium rivulare
  • Tetraplodon mnioides
  • Trichostomum brachydontium
  • Ulota bruchii
  • Ulota phyllantha
Of the mosses with a costa but no hairpoint, the majority appear to possess a costa which reaches the tip of the leaf, rather than stops short of it.

This could, perhaps, be considered the optimal arrangement of the costa from an "engineering" point of view, maximising both the strength and water transport functions of the structure.


Nerve almost reaches leaftip
  • Aulacomnium androgynum
  • Brachythecium populeum
  • Gyroweisia tenuis
  • Kindbergia praelonga
  • Mnium hornum
  • Pohlia melanodon
  • Pohlia wahlenbergia
  • Thuidium tamariscinum
Mnium hornum Mnium hornum (Mniaceae)


Mnium hornum

Costa nearly reaches tip

Mnium hornum is a very common woodland moss forming loose dull-green carpets. A closer look at a single shoot shows not only anatomical details, but also reveals great beauty.

In mosses with very small leaves, determining whether the costa reaches the leaftip or not can be difficult. However, Mnium hornum, with it's relatively large spreading leaves, shows the costa detail very clearly.

Presumably there's little difference in functionality between costas that reach, and those that almost reach, the leaf tip.


Nerve ½ to ¾ length of leaf
  • Brachythecium albicans
  • Bryum argenteum
  • Eurhynchium striatum
  • Pseudoscleropodium purum
  • Rhynchostegium confertum
Brachythecium albicans Brachythecium albicans (Brachytheciaceae)


Brachythecium albicans

Costa ½ to ¾ length of leaf

The leaves of Brachythecium albicans very much overlap one another and are appressed to the shoot, making determination of the costa length difficult. However, with good lighting you can see that the costa runs about ¾ up the length of the leaf in this species.

There appears to be few mosses with a costa in this proportion to the leaf, making it a useful diagnostic character.


Nerve about ¼ length of leaf
  • Pterygonium gracile*
Pterygonium gracile Pterygonium gracile (Leucodontaceae)


Pterygonium gracile

Costa ¼ length of leaf

Even in this close view of some shoots of Pterygonium gracile the costa cannot be discerned due to the way the leaves overlap one another. Removing a leaf for closer inspection should reveal the short costa.

There appears to be few mosses with a costa in this proportion to the leaf, making it a useful diagnostic character - if you can see it!


Double nerve present
  • Hylocomium splendens*
  • Hypnum cupressiforme*
  • Hypnum jutlandicum
  • Plagiothecium undulatum
  • Pleurozium schreberi*
  • Pterygonium gracile*
  • Rhytidiadelphus loreus
  • Rhytidiadelphus triquetris
Plagiothecium undulatum Plagiothecium undulatum (Plagiotheciaceae)


Plagiothecium undulatum

Double nerve present

Even this close view of well-hydrated leaves of Plagiothecium undulatum fails to reveal any double nerves.

Many of the species whose leaves can have a double nerve, include individuals where nerves are absent. Furthermore, the two nerves may be of different length, or one may not be developed at all in some specimens.


Costa absent (or very inconspicuous)
  • Calliergonella cuspidata
  • Ctenidium molluscum
  • Hedwigia stellata
  • Leucodon sciuroides
  • Hylocomium splendens*
  • Hypnum cupressiforme*
  • Pleurozium schreberi*
Calliergonella cuspidata Calliergonella cuspidata (Amblystegiaceae)


Calliergonella cuspidata

Costa absent or apparently so

It's pretty hard to illustrate a negative, and many mosses do have very small nerves, but in this close view of a shoot of Calliergonella cuspidata, no nerve is visible. The character would help where you are considering one of these species but note the presence of a nerve in the specimen to be determined.

Most of the common mosses, at least, have a nerve or costa, and so the absence of this character is a useful diagnostic.

It would be an interesting exercise to see if there's any correlation between moss species lacking a costa, and the environment they occupy. Avalability of moisture comes to mind, but C. cuspidata is found in wet environments while H. stellata is often found on exposed rock surfaces in elevated locations.


Teeth on leaf margins
  • Atrichum undulatum
  • Aulacomnium palustre Note:
    Teeth only present towards the tip of the leaves.
  • Bartramia pomiformis Note:
    Teeth only present towards the tip of the leaves.
  • Brachythecium plumosum Note:
    Denticulate.
  • Brachythecium rutabulum Note:
    Denticulate.
  • Breutelia chrysocoma
  • Bryum rubens Note:
    Commonly faintly toothed towards leaf tip.
  • Climacium dendroides Note:
    Branch leaves coarsely toothed towards leaf tip; stem leaves smooth.
  • Cratoneuron filicinum
  • Ctenidium molluscum
  • Dicranella rufescens Note:
    Denticulate at least above.
  • Dicranum fuscescens Note:
    Toothed towards leaf tip.
  • Dicranum majus Note:
    Sharply toothed towards leaf tip.
  • Dicranum scoparium Note:
    Variously toothed towards leaf tip.
  • Eurhynchium striatum
  • Fissidens adianthoides Note:
    Toothed towards leaf tip.
  • Fissidens dubius Note:
    Irregularly toothed towards leaf tip.
  • Hylocomium splendens
  • Hyocomium armoricum
  • Isothecium alopecuroides Note:
    Teeth only present towards the tip of the leaves.
  • Kindbergia praelonga
  • Mnium hornum
  • Oligotrichum hercynicum Note:
    Widely spaced.
  • Palustriella commutata Note:
    Denticulate below (and possibly throughout).
  • Philonotis fontana
  • Plagiomnium ellipticum Note:
    Sometimes lacking.
  • Plagiomnium rostratum
Plagiomnium rostratum Plagiomnium rostratum (Mniaceae)


Plagiomnium rostratum

Teeth on leaf margins

Marginal teeth in moss leaves are often unicellular, comprising a cell with a projecting corner as seen here in Plagiomnium rostratum. Note also the difference between the marginal border cells and those behind the leaf margin.

  • Plagiomnium undulatum
  • Pogonatum aloides
  • Pogonatum urnigerum
  • Pseudoscleropodium purum Note:
    "Lightly toothed" according to Watson, although I've not yet noted the teeth.
  • Pterygonium gracile Note:
    Dentate above.
  • Ptychomitrium polyphyllum
  • Rhynchostegium confertum
  • Rhodobryum roseum Note:
    Distantly toothed at apex.
  • Rhytidiadelphus loreus
  • Rhytidiadelphus squarrosus
  • Rhytidiadelphus triquetris
  • Thamnobryum alopecurum Note:
    At apex.
While compiling this list I noted that many mosses with teeth, bear them towards the leaf tip only, and so a separate list of these might be helpful. A further discrimination could be made in relation to the shape (e.g. sharp, blunt), spacing and relative size of the teeth (including whether they are multicellular).


Teeth on hairpoints only
  • Polytrichum piliferum
  • Campylopus atrovirens
  • Grimmia pulvinata Note:
    Lightly but distinctly toothed.
  • Hedwigia stellata Note:
    Hyaline apex bears spinose teeth.
  • Racomitrium lanuginosum
  • Syntrichia ruralis ssp. ruraliformis
Grimmia pulvinata Grimmia pulvinata (Grimmiaceae)


Grimmia pulvinata

Teeth on hairpoints only

The characteristic form of toothed hairpoints is illustrated by these leaves of Grimmia pulvinata, the teeth comprising out-turned extensions of the long hyaline cells comprising the hairpoint.

The teeth on hairpoints and hyaline tips of moss leaves, often have an appearance quite different from the kinds of teeth that are borne on leaf margins. In the latter, it's common for a marginal cell to be triangular or with a distinct kink, such that a tooth-like projection is formed. The teeth on hyaline points, on the other hand, often look like spinose projections of cell wall material.


Teeth absent
  • Amblystegium serpens
  • Amphidium mougeotii
  • Aulacomnium androgynum
  • Barbula convoluta
  • Barbula unguiculata
  • Brachythecium albicans
  • Bryum alpinum
  • Bryum argenteum
  • Bryum capillare
  • Bryum pallens
  • Bryum pseudotriquetrum
  • Calliergon giganteum
  • Calliergonella cuspidata
  • Campylopus introflexus
  • Ceratodon purpureus
  • Dichodontium palustre
  • Dicranoweisia cirrata
  • Didymodon rigidulus
  • Fissidens bryoides
  • Funaria hygrometrica
  • Grimmia laevigata
  • Gymnostomum aeruginosum
  • Gyroweisia tenuis
  • Homalothecium sericeum
  • Hypnum andoi
  • Hypnum jutlandicum
  • Neckera complanata
  • Neckera crispa
  • Orthotrichum anomalum
  • Plagiothecium undulatum
  • Pleurozium schreberi
  • Pohlia melanodon
Amphidium mougeotii Amphidium mougeotii (Rhabdoweisiaceae)


Amphidium mougeotii

Absence of teeth on leaf margins

Marginal teeth on moss leaves can be more or less conspicuous, but in Amphidium mougeotii, the leaf margins are decidedly plane.

  • Pohlia nutans
  • Pseudocrossidium hornschuchianum
  • Pseudocrossidium revolutum
  • Racomitrium aciculare
  • Racomitrium fasciculare
  • Racomitrium heterostichum
  • Rhizomnium punctatum
  • Schistidium maritimum
  • Schistidium rivulare
  • Syntrichia laevipila
  • Tortella tortuosa
  • Tortula muralis
  • Trichostomum brachydontium
  • Ulota bruchii
  • Ulota phyllantha
  • Warnstorfia fluitans
The cursory investigation made here suggests that there's as many moss species with marginal teeth as without.

Details of the leaves lists
    The moss line
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