OPHIOGLOSSUM IN INDIA – A REVIEW

Ophioglossum is one of the three taxa of eusporangiate fern family Ophioglossaceae. It is distributed throughout the world. In India more than a dozen species are known. Studies on systematics, morphology, anatomy, reproduction biology, cytology, phytochemistry and phylogeny are reviewed in this paper. Ophioglossum includes four subgenera i.e. Cheiroglossa, Ophioderma, Euophioglossum, and Rhizoglossum. Steler system is either cauline or foliar in origin. Leaf traces single or double. Ontogeny and anatomy of the common stalk and tropophyll vary with species. Sclerenchyma is absent in ground tissue. Sporangia globose eusporangiate in two rows on lateral sides of the stalked spike. Sporogenesis unique. Spores homosporous, monolete or trilete, exine ornamentation variable. Gametophytes subterranean, simple or branched, radial and bisexual. Antheridia embedded while neck of archegonium protrudes out of surface of gametophyte. Embryo development without suspensor and endoscopic except O. nudicaule which has a small suspensor and an exoscopic development. Mycorrhizic association frequent in roots, rhizome and gametophytes. Ophioglossum shows a high rate of polyploidy and chromosome numbers vary from n=30 bivalent (O. eliminatum) to n=720 bivalent (O. reticulatum). Studies on phytochemistry and antimicrobial activities have yielded interesting results. Phylogeny is discussed with Rhyniales, Coenopteridales and progymnosperms.