Hardbound, manuscript of the PhD thesis submitted to Centre for Interdisciplinary Studies of Mountain & Hill Environment, University of Delhi and Department of Botany, Zakir Husain Delhi College, University of Delhi. This thesis uses Scanning Electron Microscope (SEM) studies of Rhododendrons. It constructs the paleo-history and pleistocene glaciation in Eurasia- Northern Hemisphere region to study the diversification and taxonomic diversity in Rhododendrons.