INTRODUCTION: Since time immemorial, man's quest for medicinal agents, that alleviate his sufferings has remained unquenched. The instinctive behaviour of primitive man helped him to realise the beneficial action of plants in the treatment of various ailments. From about 11th to 18th centuries, a dogma known as the "doctrine of signatures" was almost the sole means by which man attributed medicinal value to certain plants. This dogma held that the colour, shape, habitat or other physical characteristics of a plant were indicative of its medicinal value. Thus, the worm shaped embryo of chenopodium (worm seed) suggested it to be of value as an anthelmintic, the yellow colour of Saffron served to point out its value in liver disorders, the serpentine roots (snake root) indicated that they should be useful in treating snake bite, due to soap forming property of quillaia bark it was used as detergent and so on. However, as man experimented, he found by trial and error, certain plants useful for the treatment of some of his myriad illnesses. Later through conscious rational action he gained better understanding about the medicinal properties of the plants