Volumes III and IV of this encyclopaedia provide a novel classification of the monocotyledons, a group encompassing plants of most diverse life-forms such as aquatics, terrestrial and epiphytic herbs, and tall trees. Of the 106 families now recognized 104 are treated in the two volumes, while the economically or horticulturally important grass and orchid families are relegated to two subsequent volumes. The classification followed here is based on recent molecular studies as well as on the vast body of information available on this plant group. The wealth and precision of information, but also the keys for the identification of genera and details on their properties, including distribution and diversification, make this work an important source for both the scholar and the practitioner in the fields of pure and applied plant sciences..