Structure of thallus of Marchantia and vegetative reproduction

Plant body of Marchantia is dichotomously branched with a prominent mid rib. Thallus is dark green in colour and is about 2 to 10 cms. Each labe of thallus has distinct mid rib and an apical notch, its wargin is weavry. On ventral surface on either side of mid rib present two or more rows of scales which protect the growing point. On lower side of central surface of thallus are rhizoids which are of two types smooth walled and tuber culated and do the function of fixation and absorption.

On dorsal surface cup like structures the gamma cup are present. These are special vegetative reproductive bodies. In some cases special upright branches are developed at the growing apex. These branches bear sex organs and are of two kinds antheridiospors and archegoniospores and are borne on different thalli.

Anatomy of thallus: V.S of Marchantia thallus (gametophyte) bears upper photosynthetic and lower storage region. Upper epidermis is colourless or pale green and has pores which are barrel shaped with four or five layers of cells with upper and lower opening. Pores lead with air chambous below. Each chamber opens out by a pore. From the floor of chamber, simple or branched photosynthetic filaments arise.

Ventral regions cells consist of starch grains. Some cells may have a single oil body or may be muatage. From lower epidermis arise tow types of smooth and tuberculated rhizoids and four or more rows of scales.

Vegetative Reproduction: it takes place in favourable conditions by following ways:

(i) By death and decay method: By progressive death and decay of older parts reaching dichotomy.

(ii) By adventitious branches: In some species adventitious branches are formed from ventral face of thallus or rarely from archegoniospores. Branches get detached from parent plant and continue life independtly.

(iii) By Gammae formation: this is profilic and specialized method of vegetative reproduction. The gammae which are the special reproductive bodies are produced in large number in small gemma cups. Each gemma has small stalk and multicellular discoid body. It is thick in middle and thin at margin. Most cells of gemma contain chloroplast, while few possess oil some rhizoids cells are also present. Each gemma falls on soils and in favourable conditions develops into two thallus of marchantia gamotophyte. Rhizoids are formed and then two thalli get separated. These thalli develop into two gametophytes of marchantia.