This is an essential reference for describing, measuring and classifying the foliage of flowering plants. The presented system provides long-needed guidelines for characterizing the organization, shape, venation, and surface features of angiosperm leaves. In contrast to systems focusing on reproductive characters for identification, the emphasis is on macroscopic features of the leaf blade including leaf characters, venation, and tooth characters. The advantage of this system is that it allows for the classification of plants independently of their flowers, which is especially useful for fossil leaves (usually found in isolation) and tropical plants (whose flowering cycles are brief and irregular, and whose fruits and flowers may be difficult to access). An illustrated terminology including detailed definitions and annotated illustrations is the focus of the classification system, the aim of which is to provide a framework with comparative examples to allow both modern and fossil leaves to be described and classified consistently.