Abstract
Evidence for the recognition of distinct evolutionary lines within the dicotyledons is examined. Firstly two groups, the Centrospermae and the Amentiferae, are discussed. Subsequently, a number of characters which have been thought to characterise major subdivisions of the dicotyledons are discussed. These include nodal anatomy, characters of the secondary xylem, sieve-tube plastids, pollen-grain nuclei, pollen morphology, chromosome number, androecial development, ovular morphology, cauline and carpellary ovules, and chemotaxonomy.