This work is based mostly on the descriptions given in Smith's paper "Arachis hypogxa L. Aerial flower and Subterranean Fruit" (2) and in the symposium "The Peanut. The unpredictable Legume" (3), and also on some of the author's observations. All cultivated peanut varieties belong to the species Arachis hypogxa L.; other species of the genus are not used for commercial production and may be of interest only for breeding purposes. Commercial peanut varieties can be grouped into one of three types : Virginia, Spanish, and Valencia. This grouping is done according to the distribution of vegetative and reproductive buds on the plant, and to the number of seeds per fruit. Studies were made on flower morphology, its duration and fertilization ; they indicated that all peanut flowers are potentially fertile and cannot, therefore, be classed into fertile and infertile types. A description of how the aerial flowers produce subterranean fruits is given.