ROSIDAE

subclass of flowering plants belonging to the class Magnoliopsida. Rosidae is 1 of the 6 subclasses in the class Magnoliopsida. It consists of 18 orders, 116 families, and more than 60,000 species. Rosidae includes the largest number of families of all the subclasses, although the vast majority of species belong to only 5 large orders: Fabales (18,000), Myrtales (9,000), Euphorbiales (8,000), Rosales (6,600), and Sapindales (5,400). The 18 orders that make up the Rosidae have natural affinities, except perhaps for the Euphorbiales and Rafflesiales, the former because of some similarities to the Malvales (Dilleniidae), the latter because, as parasites, they have lost certain characteristics that might otherwise clarify their affinities. Members of the Rosidae tend to be more advanced than the Magnoliidae, and the Rosidae and the Dilleniidae constitute two natural groups derived separately from that ancestral stock. The Rosidae are found in most habitats. Duane Isely subclass of woody and herbaceous dicotyledonous flowering plants. The subclass consists of 18 orders, of which the vast majority of species are found in 5Fabales, Myrtales, Euphorbiales, Rosales, and Sapindales. The subclass as a whole consists of 114 families and almost 60,000 species. The flowers of most members in the subclass contain distinct petals, rarely uniting to form a lobed corolla tube. The spirally arranged stamens are often numerous, and the gynoecium is apocarpous or monocarpous. The Rosales is considered to be the oldest order of the Rosidae and is thought to be basal to all other orders in the subclass. The remaining orders in the subclass are Proteales, Podostemales, Haloragales, Rhizophorales, Cornales, Santalales, Rafflesiales, Celastrales, Rhamnales, Linales, Polygalales, Geraniales, and Apiales. Additional reading A number of mangrove species occur in the Rosidae subclass, and they are addressed in P.B. Tomlinson, The Botany of Mangroves (1986); and Patricia Hutchings and Peter Saenger, Ecology of Mangroves (1987).