This very welcome addition to the literature on the structure and evolution of flowers provides a valuable and practical new perspective on a classical botanical theme. It focuses on the relationships between flower structure and the evolutionary diversification of plants as reflected in the latest system of classification.

Floral diagrams provide one of the best examples of the idea that a picture is worth a thousand words. They provide a stylised system for describing and communicating the arrangement of floral organs with great simplicity, regardless of the structural complexity of the particular flower. It is therefore no surprise that floral diagrams have stood the test of time and remain as effective today as when they first began to be used. The German botanist August W. Eichler is generally credited with their introduction in the late nineteenth century and they were rapidly adopted, soon becoming a familiar feature of numerous botanical textbooks. Eichler was also a pioneer in the field of classification of flowering plants and one of the first botanists to base a system of classification upon evolutionary principles. Whilst the utility of floral diagrams has remained unchanged since their invention, we now use very different methods to establish the evolutionary relationships between different groups. For most of the twentieth century plant classification relied on the comparison of morphological characters and numerous different schemes competed for attention. The advent of classifications based upon the analysis of DNA sequence data rather than on traditional morphological characters resulted in revolutionary advances.