Spore is the first cell of the gametophyte. In Dryopteris the spores are of one kind i.e. homo sporous.
The spores germinate under favorable conditions of temperature and moisture. Each spore is surrounded by an outer coat called exine and an inner coat called intine.
During germination, the outer coat ruptures and intine comes out in the form of multi cellular filaments. This when fully developed, forms a dorsiventral flat, green, heart shaped structure called prothallus with an apical notch hiding the growing point. The lobes
Of prothallus is one cell in thickness, whereas the central part lying immediately below the apical notch is several layers of cells in thickness. Several slender rhizoids develop from the ventral portion of the prothallus which helps the prothallus to attach to the substratum and draw nutrients. Being green in color, it synthesizes food by the process of photosynthesis.
ADVERTISEMENTS:
The fully grown prothallus is approximately 1/8 to 1/3 inch in diameter and is an independent plant. The prothallus is monoecious and protandrous. The male sex organs or antheridia and female sex organs or archegonia are produced on the ventral surface of the thallus.