Meiotic Studies in the GenusAdiantum

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Abstract
Meiotic studies have been made in nine species of the genus Adiantum. Some of them like A. caudatum, A. philippense, A. capillus-veneris and A. aethiopicum were collected from several localities where they were found growing in nature. Others were procured from different nurseries of India. The species A. capillus-veneris, A. caudatum, A. aethiopicum, A. trapeziforme, A. peruvianum and A. tenerum were found to be diploid with 2x = 60 while A. philippense was found to be triploid with 2x = 90, A. cuneatum a tetraploid with 2x = 120 and A. concinnum a hexaploid with 2x = 180. Pairing was found to be regular in A. capillus-veneris, A. caudatum, A. aethiopicum, A. trapeziforme, A. tenerum and A. cuneatum. The species A. peruvianum showed a number of univalents at late diakinesis, laggards at anaphase I and II and pentads. The spores in this species were of different shapes and sizes from regular well developed ones to shrunken and empty ones. Some aberrant spore mother cells with double the number of chromosomes were also found with normal pairing and regular anaphase separation. In the species A. philippense, two types of sporangia were found, one with eight spore mother cells and the other with sixteen spore mother cells. Eight celled sporangium gave rise to 32 big sized spores while sixteen celled sporangium gave 64 shrunken and empty spores. A. concinnum showed eighty univalents and fifty bivalents per spore mother cell. Numerous laggards were observed at anaphase I and II with the formation of micronuclei. Pentads were observed. Spores were of various shapes and sizes, all were empty and shrunken. As a result of the evaluation of meiotic data, tentative conclusions on the relationship of species, mechanisms of speciation and variation etc. have been drawn.

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