This book is the outcome of intensive and extensive studies persistently carried out for more than two decades both in fields of more than 8 states of maximum occurrence of species and almost all herbaria in India. Studies were also carried out in leading herbaria like Kew herbarium, Rijksharbarium Leiden, BGBM herbarium Berlin, CANB Canberra, Beijing etc. In this book, more than 10 parameters of studies are dealt with for the first time. Additionally, about 5 parameters, which previously had very little information, are provided with additional data. Thus, sufficient data on more than 15 parameters is available in the book. Another significant feature of this book is the incorporation of numerous photo plates, illustrations and tables for in-depth understanding of the genus in general. These also help in clearing up ambiguities that prevailed in earlier literature. Of particular note are photo plates of 27 taxa that provide visual aids which will help for identifying species as these photo plates depict the most representative live specimens. In view of bringing out delimitation of the variations under subspecific categories, 65 forms have been recognized which will help in further delimitations of taxa. These forms are provided with line drawings and for forms of a species, characters are provided in comparative tables. This helps to easily distinguish each form. A new classification for the genus is proposed which not only makes identification easy but is based on phylogeny of the genus based on mostly morphological features. This phylogenetic analysis is almost identical to molecular phylogeny. Relationships of species and evolutionary trends of genus are correlated and diagrammatic representation of the phylogenetic tree is provided in the concluding chapter. For easy identification an artificial bracketed key is provided. Since many species have varying time periods ranging from two to four weeks, a key based on vegetative and flowering characters is provided for tentative identification as an appendix.
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