General Principles and Methods.- Principles and Concepts in the Classification of Higher Taxa.- Delimitation of the Major Taxa of the Higher Cycadophytina: Theoretical Criteria Versus Taxonomic Practice.- Some Aspects of the Classification and Evolution of Higher Taxa.- Some Problems Associated With Character Correlations.- Biochemical Systematics: Methods and Principles.- Quantitative Studies of Inter-relationships Amongst the Liliatae.- Classification Above the Genus, as Exemplified by Gesneriaceae, With Parallels From Other Groups.- Evolutionary Aspects and Taxonomic Evidence.- The Anatomy of Secondary Xylem and the Classification of Ancient Dicotyledons.- Ovular Morphology and the Classification of Dicotyledons.- Seed Characters in and Affinities Among the Saxifragineae.- Transmission Electron Microscopy and Systematics of Flowering Plants.- On the Taxonomic Significance of Secondary Metabolites in Angiosperms.- Cyanogenic Compounds as Systematic Markers in Tracheophyta.- Some Aspects of Beetle Pollination in the Evolution of Flowering Plants.- New Ideas About the Early Differentiation of Angiosperms.- Evolution and Classification of Major Taxa.- Phyllocladus and Its Bearing on the Systematies of Conifers.- A Commentary on a Diagrammatic Presentation of the Angiosperms in Relation to the Distribution of Character States.- The Treatment of the Monocotyledons in an Evolutionary System of Classification.- Some Realignments in the Angiospermae.- Evolutionary Trends in the Hamamelidales-Fagales-Group.- Urticales, Their Differentiation and Systematic Position.- New Aspects of the Systematics of Asteridae.- Summary Lecture.- Summary Lecture.- Index to Plant Taxa.