Asexual reproduction: As stated earlier, this takes place by spore formation. Spores are produced in sporangia which develop in sori.

Sporangium (Fig. 15.4A): Each sporangium has a slender multicellular stalk and a body called capsule. The capsule is oval or circular and flattened on two lateral sides like a biconvex lens. The capsule wall is single layered and composed of thin-walled cells. There is a ring of special cells in the wall that runs around the capsule along its median edge. A major part of the ring is formed by the annulus, in which cells have very thick inner walls. The remaining part of the ring is called the stomium region. It is formed by large, thin walled delicate cells. This ring plays an important role in the liberation of spores.

Each sporangium contains 16 diploid spore mother cells. These divide by meiosis and produce 64 haploid spores (n). Nephrolepis is homosporous. All spores are small and kidney-shaped (Fig. 15.4B). The diploid sporophyte generation ends with the meiosis.

Liberation of spores (Fig. 15.4C). The spores are liberated from the capsule when the sporangium matures. The sporangium (capsule) wall breaks open in the region of the stomium and the spores are liberated through the opening. This is caused due to movements of the annulus in hot and dry conditions.

Sexual reproduction: It takes place in the haploid gametophyte generation and involves the formation of specialized male and female sex organs.

Antheridium (Fig. 15.5). This is the male sex organ. Antheridia develop on the lower surface of the prothallus in the region of posterior margin among the rhizoids. Each antheridium is sessile. It has a very small, delicate and globular body. The body wall is called jacket. It is composed of only three cells: basal cup cell, middle ring cell and apical cap cell. Antherozoids are produced in each antheridium. These are haploid male gametes. Each one has a spirally coiled body with many flagella. The wall of the mature antheridium breaks open in the presence of water, and the antherozoids are liberated on the moist soil.

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