Systematic botany deals with the classification of plants. The study is based upon the structural resemblance of plants and is helpful in identifying them. The resemblance are brought out by describing, naming and arranging the plants in a methodical manner for which a thorough knowledge of morphology is necessary.

   At first people took interest only in useful medicinal and crop plants. This naturally left out of consideration very many plants, which were not known to be either medicinal or otherwise useful. Later on, plants were classified into herbs, shrubs and trees. Still later on, Linnaeus, hailed as the father of systematic botany, gave out a classification based on the nature of stamens and pistils of flowers. This system of classification is also known as the 'sexual system'.

   There are a number of systems of classification named after the botanists who gave them out. The current system of classification are those of Benthem and Hooker. Engler, Bessey, Hutchinson and Tippo. The system of 'Benthem and Hooker' is often followed in British Commonwealth, Engler's in Europe and the Eastern half of USA and it is true that none of them can claim to be a perfect system. It may be stated that all of them serve as good keys for the purposes of identification of any given plant.

   Mostly herbs, with alternate or tufted basal leaves. Sepals are usually 4 or 5, coloured when petals are absent. Stamens are many. Ovary consisting of many independent carpels maturing into 'achenes' or 'follicles'.

  Distribution: They are abundant in temperate and cold regions; there are about 30 genera and the known species are about 300.

    Tree, shrubs or herbs. Leaves are alternate simple entire or toothed. Flowers are yellow or white, often showy. Sepals and petals each 5 and the latter are soon falling. Stamens are many. Carpels are 1 or more, free or joined together. Ovules one or more in each carpel.

    Distribution :They are chiefly tropical and the species are about 200.