This is the fourth volume in The Illustrated Flora of Illinois devoted to dicotyledons, or dicot plants. Dicots are the greatest group of flowering plants, exceeding the monocotyle dons, or monocots. Dicots produce a pair of seed leaves during germination while monocots produce only a single seed leaf.

This volume contains four orders and ten families of dicots. The orders included in this volume are Malvales, Urticales, Rhamnales, and Euphorbiales. Within the Malvales are the families Tiliaceae, Sterculiaceae, and Mal vaceae. The families Ulmaceae, Moraceae, and Urticaceae comprise the Urticales. Rhamnaceae and Elaeagnaceae make up the Rhamnales. The Euphorbiales include only the Thymelaeceae and the Euphorbiaceae.