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Cytological studies in the Tasmania conifers, the Indian Scilia and dipcadi

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Rao, YS 1959 , 'Cytological studies in the Tasmania conifers, the Indian Scilia and dipcadi', PhD thesis, University of Tasmania.

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Abstract

There has been a considerable speculation with regard to the systematic and phylogenetic position of the Tasmanian endemic Conifers in the so-called "Taxares" and "Pinares". Restricted to alpine terrains at an altitude of 3,500-4,500ft., they bear a superficial resemblance although belonging to different families per se. In any scheme of Conifer phylogeny based on external characters alone, allocation of these genera to their proper systematic position would be difficult. Previous cytological studies were wholly confined to the reports of chromosome numbers of two genera. In the first part of this dissertation an attempt has been made not only to provide detailed information about their karyotypes but also to critically evaluate and integrate the karyological data with the available knowledge of their comparative morphology. The ultimate object is to assess the phylogenetic status of the Tasmanians Conifers. Two methods that enabled a critical study of their somatic chromosomes have been outlined in the second part.
The probable trends in evolution of the two Indian Liliaceae namely Dipcadi and Scilla have so far not received any detailed consideration. The species of Dipcadi exhibit considerable convergence in their morphological characters; the area of the genus is wide and at the same time highly disjunct; several of its species are endemic. Providing a cytological basis for all these features has been the aim of the third paper. The mode of origin of the different cytotypes, the prevailing differences between the local populations in their meiotic behaviour, the potentialities that are in store for further evolution and speciation within a collective species like Scilia indica have been outlined in the fourth section. The variation in the heterochromatin content of the different individuals of S. hohenackeri has also been appended to the same paper.

Item Type: Thesis - PhD
Authors/Creators:Rao, YS
Keywords: Conifers, Cytology
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Copyright 1959 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

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Thesis (PhD)--University of Tasmania, 1959

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