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Riccardia palmata
Riccardia palmata

Some liverworts are extremely small, such as the patch of Riccardia palmata colonising this tree stump in a wood east of Alford in Aberdeenshire.

Riccardia palmata

Under the lens the individual shoots become apparent, but to the naked eye the green patch on the stump could be mistaken for a green algal community.

Liverwort leaves
Liverworts show diversity in some features which in mosses tend to be uniform.

While the range of structures in liverwort leaves is less varied than that of mosses, in particular there's never any development of a costa or nerve, the outline of leafy liverwort leaves shows great diversity. In some species there's relatively wide lobes or narrower finger-like projections, others have sharp-pointed cusps or notches. Finer features include spine-like protrusions, teeth and hairlike fringes.

Another area where liverworts "excel" in terms of morphological diversity is in the range of form in underleaves and lobules.

Boquhan Burn
Boquhan Burn

Here's a typical Scottish habitat where bryophytes will be found in some abundance. The damp crevices in the rocks may be home to leafy liverworts while flat areas of rock close to the water are likely niches for thallose liverworts. Boquhan Burn, near Kippen, Stirlingshire.

Simple, margin entire
  • Jungermannia excertifolia
Jungermannia excertifolia Jungermannia excertifolia (Jungermanniaceae)
Jungermannia excertifolia

Simple leaf edge

This is Jungermannia excertifolia ssp. cordifolia, a leafy liverwort with rounded entire leaves.

I guess you could consider leaves with a simple leaf margin the "default" situation, with all other projections and notches as superimposed variations.

With two cusps
  • Lophocolea bidentata
  • Nowellia curvifolia
Nowellia curvifolia Nowellia curvifolia (Cephaloziaceae)
Nowellia curvifolia

Two cusps

Seen with the naked eye, Nowellia curvifolia appears almost like some millipede, the minute cusps like thousands of tiny legs.

In both the species listed here, the leaves bear two horn-like projections, each sharp point of which tends to point towards the other.

With three cusps
  • Bazzania trilobata
There aren't many liverworts with three cusps on the leaves but hopefully I'll come across Bazzania trilobata in my travels.

With four or more cusps
  • Barbilophozia spp.
  • Lepidozia reptans
Lepidozia reptans Lepidozia reptans (Lepidoziaceae)

Lepidozia reptans

Four or more cusps

The obliquely-inserted leaves in the patch of Lepidozia reptans here can clearly be seen to be incubous, even though few of the leaves actually overlap one another.

There are few liverworts in Britain and Ireland whose leaves have four or more cusps, and the leaves in the species listed here are extremely small, so that under low magnification the leaves look just a little bit "hairy" rather than bearing cusps.

Conspicuous underleaves
  • Bazzania trilobata
  • Calypogeia fissa
  • Calypogeia muellerana
  • Frullania dilatata
  • Frullania tamarisci
  • Porella cordeana
Porella cordeana Porella cordeana (Porellaceae)

Porella cordeana


The photo here of Porella cordeana doesn't show the underleaves very clearly, unfortunately. I'll post a better example later.

Viewed from above, many liverworts appear to have shoots with a simple leaf arrangement of two rows of overlapping leaves. However, in many species, looking at the underside reveals further complexity including underleaves (which can vary in size and shape from the leaves on the top surface of the shoot), and lobules or amphigastria (folds in the leaves which can give the impression of further rows of leaves).

Conspicuous lobules
  • Diplophyllum albicans
  • Frullania dilatata
  • Frullania tamarisci
  • Porella cordeana
  • Radula complanata
  • Scapania nemorea
Frullania tamarisci Frullania tamarisci (Frullaniaceae)

Frullania tamarisci


For this photomicrograph of Frullania tamarisci I used mostly transmitted light, creating something like an X-ray of the shoot to reveal something of the complex structure.

Frullania tamarisci has both underleaves and lobules, both structures that you'd expect would be more concerned with moisture retention than photosynthesis.

With teeth or spines
  • Plagiochila spinulosa
Plagiochila spinulosa Plagiochila spinulosa (Plagiochilaceae)

Plagiochila spinulosa

Spines on leaves

The leaves of Plagiochila spinulosa bear a few intermittent sharp projections that are more like spines than teeth.

In vascular plants we generally consider spines to be deterrents against browsing animals eating foliage, but given the softness and size of spines such as those in Plagiochila spinulosa, it's hard to envisage any useful role for these structures.

Fringed margin
  • Ptilidium ciliare
  • Trichocolea tomentella
Trichocolea tomentella Trichocolea tomentella (Jungermanniales)

Trichocolea tomentella

Fringed margin

At lower magnifications, the fringed margins of the leaves in Trichocolea tomentella convey a "furry" look to the shoots.

Some liverworts have a fringe of fine hairlike projections on the leaf margin, giving an appearance of a frilly margin.

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