The genomic constitution of the genus Ophioglossum is complicated because of its being geologically ancient and of long evolutionary history. A lot of plants of the same and different species resemble each other as well as show significant differences among morphological characters among themselves. Many of the new species described have exhibited several unknown features not observed in any species of the genus so far. In this paper, we wish to emphasize that mere observations on shape and size of trophophyll (leaf) and rhizome, should not be taken reliably in delimiting different species of the genus Ophioglossum because of several variations already reported for many species. Preference should be given to exine ornamentation of spores as emphasized by the present study. Detailed observations on exine ornamentation of spores under SEM have offered precious and distinctive features; semi-tuberculate, beaded strings, and stripped exines are a few forms of spore ornamentations offering clear distinction among species. Long chains of circulate-alete (round alete) spores, sometimes linear tetrads as described hereunder in Ophioglossum aletum are novel features exclusively confined to this species. Comparative chromosome profiles of many species described earlier do not offer any significant support to the identity except in O. eliminatum, which has the lowest chromosome count (n = 90). This appears that since almost all species possess intraspecific polyploidy, the intragenomic variability must be loaded with interspecific hybridization contents including chromosomal aberrations. Quite possibly, this may be one of the reasons that homologous chromosomes rarely form trivalents and multivalents during early meiotic stages, despite the fact that palaeoautoploidy must have resulted in copying homologous chromosomes. In recent years, repeated phylogenetic analysis of chloroplast rbcL have revealed that many species in India appear to be offshoots of a vulgatum clade which are likely to be the hybridization products involving O. costatum, O. vulgatum, O. reticulatum, and also including of other interspecific hybridizations. It is remarkable to mention that some of the new taxa published by us, viz. O. eliminatum, O. indicum, O. aletum and O. chalonerii (unpublished), explicitly show distinct phylogenetic relationship maintaining independent genomic identity. Furthermore, each new species shows some rare uniquely confined trait not possessed by any other species of the genus. These morphological traits also suggest that the plants may be expressing extremely rare genic-combinations which might have been brought forth due to autopolyploidy and/or allopolyploidy (hybridizations) during the past few decades. Obviously, we will need a multidisciplinary approach (morphological, anatomical, biochemical) in order to identify different species of Ophioglossum with new and unusual genomic identity and also to understand possible evolutionary mechanisms undergoing within the genome.
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