10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 1 2014 (January - March) lessThan i greaterThan Actiniopteris radiata lessThan /i greaterThan (Swartz) Link. is a fern belonging to the family Pteridaceae. The spores collected from the pinnae of lessThan i greaterThan A.radiata lessThan /i greaterThan was inoculated in Knudson's C and Knop's medium at pH 5.8. The ontogenic pattern such as germination type, prothallial development and micromorphological changes were studied in detail. The germination of the spore was lessThan i greaterThan Anemia lessThan /i greaterThan type. The gametophyte development was lessThan i greaterThan Ceratopteris lessThan /i greaterThan type. The growth area in Knudson's C medium(KC), Knop's (Kn) medium and brick pieces supplemented with Knudson's C medium showed different germination percentage, growth area and micromorphology. In micromorphology, the apical notch formation varied in different medium. Few antheridiate prothalli could be seen in Knop's medium. R. MANONMANI AND S. CATHARIN SARA Actiniopteris radiata, in vitro spore germination, ontogenic stages of development. 483-491