The term genome, the basic gene complement of an individual, is almost synonymous with the chromosome complement of both nucleus and organelles. Refinements in cellular, genetic and molecular methods in recent years have opened up unexplored avenues in genome research. The modern tools of gene and genome analyses, coupled with analysis of finer segments of gene sequences in chromosomes utilizing molecular hybridization, are now applied on a wider scale in different groups of plants, ranging from algae to angiosperms. The present series on Plant Genomics: Biodiversity and Evolution aims to cover, in successive volumes, comprehensive reviews, concepts and discussions on the results of genome analysis and their impact on systematics, taxonomy, phylogeny and evolution of all plant groups. This volume touches upon the Lower Groups of plants.