A comprehensive manual lays out a morphological and comparative framework for plant classification, explaining principles that regard simpler, more complete forms as older and reduced or specialized forms as younger. It gives ordered treatments of Thallophyta, algae, fungi, and vascular plants, presenting diagnostic keys, structural descriptions, and taxonomic sequences that emphasise relationships and progressive reduction. Technical terminology for floral and vegetative organs is defined for consistent use, and recent revisions of algal and fungal groups are integrated. Numerous illustrations and appendices compare earlier classification systems and provide tabular keys to support identification and teaching.