Leafy Liverworts

Note

Key to sections

1 Habit prostrate and creeping, densely matted; stems pinnately branched — Section 1

Habit various; branches few and irregular, not pinnate — 2

2 Leaves unequally divided into 2 lobes, the small (dorsal) lobe lying flat across the larger (ventral) one, or reflexed, thus some- times giving impression that leaves are in 4 ranks — Section 2

Leaves symmetrically 2-cleft or 3-cleft — Section 3

Leaves simple and rounded, their margins either entire or with numerous minute teeth — Section 4

SECTION 1

1 Robust, larger branches 2 mm. across — 2

More slender, branches 1 mm. across or less — 3

2 Plant olive green to reddish brown leaf lobes fringed with long teeth or ‘cilia’,— Ptilidium ciliare

Plant deep green when dry, vivid green when moist, no cilia; underside of shoot gives impression of leaves in 5 ranks — Porella platyphylla

3 Plant dull or dark green, leaves so minute (0.2 – 0.3 mm.) that it is only just possible to see with 10 x lens that each is divided into 3-4 finger-like lobes, shoots lacking obvious dorsal and ventral surfaces — Lepidozia replans

Plant brownish olive or deep coppery red-brown; each leaf bipartite (a rounded dorsal lobe and a minute ventral sac), dorsal and ventral surface clearly marked; branches appearing as if clothed with overlapping scales — 4

4 Colour olive to dull reddish brown; shoots slender (about 0.5 mm. across); widely distributed, chiefly on trees — Frullania dilatata

Colour deep coppery red-brown, shining when dry; shoots about 1 mm. across; a conspicuous species on rocks and trees in west Britain — F. tamarisci

SECTION 2

1 Each leaf divided to near base into 2 narrow oblong segments, causing leaves to appear to be in 4 ranks; very common olive green to brownish plant of acid banks, etc. — Diplophyllum albicans (Diplophyllum obtusifolium is similar but without a 'nerve')

Each leaf divided to about 2/3 or less, the segments round or nearly so, not narrowly oblong; colour and habitats various.— 2

2 Shoot tips bearing conspicuous clusters of reddish brown gemmae — Scapania nemorosa

Clusters of brown gemmae lacking —3

3 In mountain springs, on dripping ledges or on rocks by mountain streams; colour most often purple-red, sometimes vivid green — Scapania undulata

Some other habitat; purple-red colour never found — 4

4 Leaf segments rounded, the dorsal one reflexed; a robust and conspicuous yellowish or olive-brown liverwort of rocky banks in mountain country Scapania gracilis

Leaf segments pointed, the dorsal one not reflexed; a slender yellowish green species of wet ground, banks, etc. — Scapania irrigua

SECTION 3

1 Tip of each leaf cleft into 3 small but distinct teeth,( the leaf itself is not symmetrical); very robust olive-green species of mountain woods, etc. (shoots up to 5 mm. across) — Bazzania trilobata

Leaves symmetrically 2-cleft, either showing 2 shallow teeth at apex only, or more deeply divided — 2

2 Leaves transversely or slightly obliquely inserted on the stems —3

Leaves very obliquely to almost longitudinally inserted — 4

3 Reddish brown plant very common on wet, mountain rock- ledges, etc.; gemmae lacking — Marsupella emarginata

Green plant widely distributed on soil pale green clusters of gemmae conspicuous at tips of stems and upper leaves — Lophozia ventricosa

4 Leaves very minute (0.3-0.6 mm.); plant forming light green or dun. green wefts on acid soil, the erect perianths alone being conspicuous to the naked eye Cephalozia bicuspidate

Leaves larger; individual leafy shoots readily seen with naked eye — 5

5 Leaves narrowed at apex, where 2 small teeth appear very close together. giving effect of minutely notched tip; plants of wet peaty surfaces, etc. — Calypogeia spp (photo is C. integristipula).

Leaf teeth relatively long and set wide apart, so that leaf has two-pronged appearance; habitat not as above — 6

6 Shoots not above 2 cm. long; some leaves entire, others 2-pronged; on bark of decaying logs; usually fertile — Lophocolea heterophylla

Shoots 2-5 cm. long; all leaves 2-pronged; among grass on banks, etc.; almost always barren — L. bidentata

(N.B. A third species, L. cuspidata, has all leaves 2-pronged and is common on decaying logs, etc. It is usually fertile but otherwise is sometimes difficult to separate in the field from L. bidentata.)

SECTION 4

1 Shoot laterally compressed, especially near tip, so that the 2 ranks of leaves appear together on one side of the stem — 2

Shoot dorsi-ventrally compressed, the 2 ranks of obliquely inserted leaves lying more or less flat, one on each side of the stem — 4

2 Robust (shoot 3 mm. wide), variegated yellow-green and purple-brown, forming conspicuous erect tufts on mountain banks and ledges Mylia taylori

More slender (shoot 1-1.5 mm. wide) — 3

3 In Sphagnum bogs; shoots long and slender, with numerous flagella branches that appear leafless — Odontoschisma sphagni

Other habitats; shoots short and crowded; flagella branches lacking — Nardia scalaris (N.B. Plectocolea crenulata is another common species that will 'key out' here. It differs from Nardia scalaris in having the leaf bordered with a row of large cells, and in other details not easily seen with a lens.)

4 Leaves with one margin strongly decurrent, succubous; robust plant (shoot up to 5 or 6 mm. wide); on the ground in moist woods, on limestone walls, etc. — Plagiochila asplenioides

Leaves not decurrent, incubous; plant more slender (shoot 2-3 mm. wide); on moist peaty banks, sides of ditches, etc. — Calypogeia trichomanis

(N.B. Chiloscyphus polyanthus is another common species that will 'key out' here. It has entire leaves, whereas the leaves of Plagiochila asplenioides are usually distinctly toothed.)

Bazzinia trilobata

Note

This section of the key has not yet been altered in respect to the orginal key by Watson.

For a more up-to-date key see the British Bryological Society online field guide.

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