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Liverwort characters
Arrangement of the leaves
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The character categories and their possible forms are:

Underleaves
underleaves

Many leafy liverworts have two rows of leaves opposite one another, and a third row of smaller underleaves borne below. The liverwort here is viewed from below in a mix of transmitted and reflected light, showing the complex outline that can result from the shape and folding of the various leaves on the shoot.

A work in progress
Liverworts proving difficult

A comparison of these liverwort pages with those dealing with mosses shows that I have much more work to do to make the character lists for liverworts more comprehensive. I've also noticed that their characters are more difficult to categorise into more or less mutually-exclusive groupings, compared to the case of mosses. This is perhaps in part a reflection of the distinct evolutionary trajectories taken by the mosses and the liverworts.

Distichous
  • Diplophyllum albicans
  • Frullania tamarisci
  • Lophocolea bidentata
  • Plagiochila asplenioides
  • Plagiochila spinulosa
Diplophyllum albicans Diplophyllum albicans (Scapaniaceae)
Diplophyllum albicans

Distichous shoots

Liverworts with conspicuously distichous leaf arrangement, such as this Diplophyllum albicans, often form expanses of loose carpets, each shoot held a little distance above those below.

Many leafy liverworts have a distichous leaf arrangement, where two rows of leaves are borne, one on either side of the shoot and held in one plane. The species included in the above list, however, are only those liverworts where the distichous arrangement is very apparent to the naked eye.


Three rows of leaves
  • Frullania dilatata
Nowellia curvifolia Frullania dilatata (Frullaniaceae)
Nowellia curvifolia

Three rows of leaves

This image of Frullania dilatata shows mostly the adaxial surface of the shoots and so the underleaves are not visible. I'll replace this image with a better illustration later.

Many liverworts have three rows of leaves, two in a distichous arrangement and the third row beneath. In most species, the latter row comprises small to very small leaves, compared to the leaves in the other to rows. The list above only includes species where the underleaves are conspicuous.



Transverse leaf insertion
  • Marsupella sp.
The leaves in leafy liverworts can be inserted (i.e. arranged on the shoot) obliquely or transversely. The latter arrangement means the leaves project at right-angles from the shoot.



Incubous
  • Calypogeia sp.
  • Radula complanata
Calypogeia Calypogeia sp. (Calypogeiaceae)


Calypogeia

Incubous leaf insertion

It's not always obvious whether a liverwort with oblique leaf insertion is succubous or, as here in a species of Calypogeia, incubous.

Incubous leaf insertion means that the leaves overlap such that the forward edge of each leaf lies on top of the back edge of the leaf in front of it. And so if you turned a shoot upside-down, the leaves would be stacked like tiles on a roof.



Succubous
  • Jungermannia excertifolia
  • Plagiochila asplenioides
  • Plagiochila spinulosa
  • Scapania nemorea
Plagiochila asplenioides Plagiochila asplenioides (Plagiochilaceae)


Plagiochila asplenioides

Succubous leaf insertion

In succubous leaf insertion, the junction of leaf and shoot lies at an angle, so that the rear leaf margin is further from the substrate than the forward leaf margin. Plagiochila asplenioides shows this clearly.

Leafy liverworts with the leaves overlapping like the tiles of a roof, i.e. the upper part of each leaf covered by the base of the next higher one, have what is called a succubous leaf insertion.



Widely-spaced leaves
  • Lophocolea bidentata
Lophocolea bidentata Lophocolea bidentata (Lophocoleaceae)


Lophocolea bidentata

Widely-spaced leaves

The leaves in Lophocolea bidentata do often ovelap one another with the front edge of each leaf lying under rear edge of the next. This makes more obvious that the species has a succubous leaf insertion.

Whether or not the leaves overlap in a leafy liverwort may not be a very formal character, but it may aid identification. In Lophocolea bidentata the junction of leaf with stem is oblique, with the rear part of each leaf further from the abaxial (lower) side of the shoot than the front part of each leaf, i.e. the leaves are inserted in a succubous arrangement.

    Arrangement of the leaves character table       View these data from a taxonomic viewpoint with notes on substrate and habitat
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    The liverwort line
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