ONTOGENY AND STRUCTURE OF THE FLOWER AND FRUIT OF PERESKIA ACULEATA

Abstract

Flowers of P. aculeata are perigynous. The receptacle cup bears a series of lanceolate bracts, which become reflexed in the fruit, and its rim bears a series of small, triangular bracts, which are sharply delimited from the perianth segments. Vascular anatomy indicates that there is a short floral tube formed by the adnation and connation of the bases of the stamens and perianth segments. The inner side of this floral tube forms an extensive cylindrical nectary; the outer side is adnate to the receptacle. There are usually five carpels, each bearing a single ovule. Carpel tips are free, but their bases are congenitally connate. During ontogeny, the adaxial faces of the carpels grow together, forming a solid style. The base of the ovary is partially divided into locules by small partitions, which represent the fused margins of connate carpels. The tip of the floral receptacle (residual meristem) becomes a convex body which enlarges in the fruit, filling that portion of the ovary cavity not occupied by seeds. The superior ovary and the columella formed in the fruit are probably primitive characteristics, but in all other respects the flower of P. aculeata appears to be advanced. It is a product of evolutionary reduction.