Formation of female spore:
Unlike seeds, spores are an asexual method of reproduction in plants. However, as plants evolved and began to adapt to a land environment, plants began to form seeds rather than spores.
(i) Nucellus is the main part of an ovule,
(ii) A female spore mother cell (2n) or megaspore mother cell is formed inside the nucellus which produces four female spores (n) through meiosis
(iii) Usually one out of four spores grows up and the rests are degenerated
(iv) The female spore is haploicd (n) and uninucleated.
(v) The transition from sporophyte to gametophyte requires the formation of haploid cells (spores) by meiosis, a process called sporogenesis.
(vi) Water is required to begin the fertilization process, so the sperm and eggs must wait for rainfall.