Observations made on the fruit development of wild species of peanut, Arachis monticola and A. villosa var. correntina, received from Argentina, are described in this paper. The ovary is uniloculaled and has two ovules. Fertilization is normal, the embryo and endosperm developing in the same way as in the cultivated peanut, Arachis hypogaea L. In more than 50% of cases both ovules develop normally, nevertheless abortion of the apical ovule is frequent and may occur in any phase of its development. In the firs case the fruits have two normal seeds; in the second, they have only one, the other being small and shrivelled. Fruits of the two species possess the two seeds separated by a sharp constriction or isthmus; this isthmus is anatomically a peg; it is dry in the ripe fruit and may be easily broken when the fruits are picked at harvest, giving then the erroneous impression that these are one-seeded. Burkart (2,3) and Hoehne (6) described a similar type of fruit for the species Arachis villosa Benth. and A. pusilla Benth.; fruits of the same type were also found by Gregory (1,8) in A. glabrata Benth. and A. hypogaea L. In addition to A. monticola and A. villosa var. correntina the writer found catenate fruits on specimens from a collection of wild species, as follows; A. Diogoi Hoehne f. typica Hoehne, A. glabrata Benth., A. pusilla Benth., A. marginata Gardn. (according to Burkart), A. prostrata Benth. (according to Burkart), A. villosulicarpa (according to Krapovickas), Arachis sp. (probably Arachis Diogoi Hoehne sub-species major Hoehne), and Arachis sp. (one unclassified species). Based on the facts that all these species have one uniloculated ovary with two ovules and the same type of catenate fruit, it seems reasonable to assume that fruit development in these wild peanuts is similar to that of Arachis monticola and A. villosa var. correntina as described in this paper.