Frosombronia_ morphology, anatomy and reproduction

Stem Anatomy: Stem T.S. shows that it consists of two zones viz. outer cortical and inner medullary region. The cortical region is chlorophyllose. It is 1-2 stratose thick and consists of slightly strongly thick walled cortical cells with brownish wall. The medullary region shows differentiation into a small central core of small celled tissue constituting al ill-defined central strand surrounded by thick walled celled medulla. Cells of the central strand lost their protoplasmic contents and are empty. They are colourless, elongated and have delicate walls. In some species of Takakia several minute spherical oil bodies are present in leaf and stem cortical cells. These oil bodies are smaller than chloroplast e.g. T. lepidozioides & T. ceratophylla. Reproduction: Takes place by vegetative and sexual process. 1-Vegetative Reproduction: In T. lepidozioides the freely eadicpis leaves and shoot and in T. ceratophylla the upper portion of shoot helps in vegetative reproduction. These parts are taken away either by wind or water and there they propagate and produce new population. 2-Sexual Reproduction: It is dioecious or heterothallic. Morphologically there is no difference among between male and female plants. Antheridia: They are present in the axil of leaves, bright orange and ellipsoidal in shape. Stalk is ill-demarked and is made up of 3-4 tiers of 4 cells each. Dehiscence of antheridium is via a cap or lid. Development of antheridium is in centrifugal pattern, where apical cell is not utilized or consumed in its formation, leading to further growth of male shoot. Archegonia: Single archegonium is present in the female plant; sometime number varies 2-3 which are irregularly scattered. Archegonium is naked, large and green when young and stalked. Venter is fleshy and becomes stratose prior to fertilization. Sporophyte is unknown. Fertilization: In antheridia the sterile jacket haploid flagellated sperms are formed. Water is required for transfer of the motile sperm to egg. Most antheridia are in terminal disk-shaped clusters to facilitate water capture for sperm transfer. Sperms are chemotactic and swim through free-water up a concentration gradient of the chemotactic agent to find the open archegonium. The first drop of water landing in the cup causes the cap cell of the antheridium to burst providing an opening for sperm into the drop of water. The next raindrop to land in the splash cup will splash out a solution containing sperm. These will swim through a film of rainwater to fuse with the egg All cells of the archegonium, including the egg cell, are produced by mitosis of haploid gametophyte cells. The disintegrating neck and ventral canal cells provide chemicals involved in sperm chemotaxis to fuse with the egg. After fusion of egg and sperm, zygote is formed which is diploid. After fertilization, the sporophyte grows out of the archegonium, and nutrients for the developing sporophyte are provided by the gametophyte. Sporophyte: The sporophyt

1. Fossombronia

2. Systematic Position

3. Occurrence gametophytes differentiated into stem and lateral leaves. Growth of the gametophyte is initiated by a single apical cell. Fossombronia is represented by about 50 species showing worldwide distribution. Four of its species reported from India are F. indica, F. himalayensi s , F. cristula and F. foreavii . In India, Fosombronia has been reported from south India, Himalayas, Pachmarhi (MP) and Kodaikanal .

4. Morphology The gametophytic plant body is foliose. The thallus is almost completely prostrate with a sparse or profuse branching. Each branch is made up of a well-developed stern bearing a single row of leaves along both the lateral margins. The arrangement of leaves becomes less organized in some species because of the greatly convoluted margins of their leaves The leaves are 2- to 3-cells thick at the base while their upper portions are only one cell in thickness. The well- developed massive stem shows no indication of any ’internal differentiation ‘of tissue. Only smooth-Walled rhizoids are present on the ventral surface of stem. The apex of the branch contains many multicellular mucilaginous hairs. Their function is to protect the apical region. Older parts of the stem do not bear any mucilaginous hairs.

5. Reproduction