Thallose liverworts

Note

1 Upper surface of thallus with diamond-shaped markings, in the centre of each diamond-shaped area a more or less raised pore 2

Upper surface of thallus without such markings and pores 4

2 Gemmae present in goblet-shaped receptacles Marchantia polymorpha (gemmae, female sporangia)

Gemmae present in crescent-shaped, ledge-like receptacles Lunularia cruciata

Gemmae absent 3

3 Pores on dorsal surface of thallus easily visible to naked eye; thallus not purple-brown at margin, ventral scales not over- lapping one another Conocephalum conicum

Pores on dorsal surface hardly visible to naked eye; thallus purple-brown at margin, ventral scales overlapping one another Preissia quadrata

4 Plants growing in pale green rosettes on arable land, etc. Thallus branches with pronounced median grooves Riccia spp.

Plants deep or vivid green; habit various; .thallus branches without pronounced median grooves 5

5 Thallus less than 2 mm. broad 6 Thallus 3-10 rom. broad (even broader at times in Anthoceros) 7

6 Midrib present and well defined; chiefly on trees Metzgeria furcata

Midrib lacking or at most ill defined; in marshes, etc. (never on trees) Riccardia spp.

7 Midrib well defined, obvious in ventral view or transverse section Pellia spp. (P. epiphylla by far the commonest, also Pellia endivifolia)

Midrib not well defined 8

8 Thallus broad (up to 1-3 cm. at times), texture thin and delicate; plant forming dark green rosettes; capsule long and narrow (up to 3-5 cm.), 2-valved Anthoceros spp.

Thallus narrow (not more than 6-8 mm. wide), thick and brittle in texture; not forming rosettes; capsule ovoid, 4-valved Riccardia pinguis

Pellia epiphylla

Note

This section of the key has been little altered in respect to the orginal key by Watson.


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