This textbook focuses on different organisms studied by students of botany. The contents have been organized in 'self-contained' units for ease of understanding. The initial chapters deal with fundamental aspects of diversity, its relevance and classification. The organisms are then analyzed, with emphasis on the important characters and systems of classification for each category of organisms. The information has been provided in a conceptual manner rather than describing representative examples of different kinds of organisms. An evolutionary approach has been adopted in presenting the information, beginning with the prokaryotic 'viruses and bacteria', journeying through 'algae', 'bryophytes', 'pteridophytes', 'gymnosperms' and culminating with the 'most visible components of the plant world the angiosperms'. During this journey, it was not possible to leave behind the 'fungi'. Although this fascinating group of organisms is no longer classified in the plant kingdom, it continues to find space in textbooks of botany.