In this article we will discuss about the morphology of marchantia with the help of diagrams.
This is a cosmopolitan genus with about 65 species, of which M. polymorpha is the best known and most widely distributed. In India, it has about eleven species, distributed all over the Himalayan region; eastern Himalayan region, in particular, supports the luxuriant growth of this liverwort.
Marchantia also occurs in hilly regions of southern India. The plant prefers moist shady places either on forest floor, or banks of streams, or shaded cliffs.
Vegetative plants with characteristic gemma cups (Fig. 2.6A) can be collected all over the year but sexual plants bearing characteristic sexual receptacles – antheridiophores (Fig. 2.6B) and archegoniophores (Fig. 2.6C) – can be collected from March to May in Himalayan region and during October-November from hills of south India. Sexually Marchantia is a long-day- plant.
The plant body is a prostrate thallus (Fig. 2.6A-C), a dorsiventral structure, which branches dichotomously. The thalli are fairly large extending up to 10 cm or more in length with a distinct midrib; represented by a shallow groove on the dorsal side and a projection on ventral side.
Present on the dorsal surface along the midrib are characteristic cup-shaped structures (Fig. 2.6A), bearing asexual reproductive propagules (gemmae), hence the name gemma- cup. The margin of a cup can be smooth, dentate or frilled – a feature, helpul in delimiting different species.
On the dorsal surface of the thallus are seen distinct polygonal areas that indicate the boundaries of underlying air chambers; each area is small with a distinct pore in the centre, which leads to an air chamber of the thallus (Fig. 2.7C).
On the ventral surface of the thallus are rhizoids and scales (Fig. 2.6D). The rhizoids, simple and tuberculate, form a dense tuft along the midrib. Scales are prominent structures on each side of midrib. Of common occurrence are two rows of scales on each side but in M. polymorpha there are three rows of scales on each side.
These scales, from centre outwards, are designated as median, laminar and marginal. Of these, the median scale is with an appendage. Other scales are simple. Each scale is membranous one-cell thick structure (Fig. 2.6D), with mucilage papillae. On its margin and main body are scattered oil cells.