Fruit (pericarp and seed) ontogeny of Sida species

Abstract

Fruits (pericarps and seeds) of the weedy species Sida rhombifolia L., S. urens L. and S. regnellii R. E. Fr. were analyzed structurally using light and scanning electron microscopy. The yellowish brown calyx is persistent on the mature fruit and consists of a crystalliferous hypodermis with U-shaped wall thickenings and homogeneous mesophyll. Fruits are schizocarpic, of the subtype coccarium, with a fibrous endocarp. Seeds are exotegmic and the embryos are clearly bent, with folded cotyledons. Structural features that are potentially significant to species’ characterization are the structure of the ovary, the morphology of the mericarp apex, the pattern of the reticulate sclerenchymatous endocarp and the presence or absence of nonglandular trichomes in the hilum and funiculus of the seed.