d) The Gametophyte

The gametophyte represents the sexual  haploid generation in the fern life cycle. The haploid generation begins after meiosis  in diploid spore mother cells. The adult gametophyte is called a fern prothallus. It is produced on moist, cool and shady soil, when a spore (n) germinates under favorable conditions.

Figure 15.3 Mature fern prothallus (lower surface view)

The prothallus is very small (about 0.5-2.0 cms in diameter), delicate and almost transparent. It is heart-shaped (Fig. 15.3) and flat with dorsoventral symmetry. The prothallus has a deep apical notch. An apical cell (growing point) is situated in the notch. The central part of the prothallus is fleshy and is thick because of a number of cell layers. This is called the cushion region. The peripheral part has only one cell layer and is called the margin. Numerous hair-like rhizoids develop from the lower surface of the posterior margin region. Rhizoids help in fixation and absorption. The cells of a prothallus contain chloroplasts. Therefore, it is photosynthetic and independent.

The prothallus (gametophyte) produces male sex organs (antheridia) and female sex organs (archegonia) during sexual reproduction. These develop on the lower surface facing the soil.

The fern life cycle shows both asexual and sexual reproduction. Asexual reproduction takes place in the sporophyte (diploid) generation while sexual reproduction takes place in the gametophytic generation.

Table of Contents

15.0 - Introduction
15.1 Pteridophyta : General Account
15.2 Gymnosperms
15.3 Angiosperms : Dicotyledons
15.4 Angiosperms : Monocotyledons
15.5 Vascularization
15.6 Development of seed habit
15.7 Development of Flower and Fruit

Chapter 16