Studies on seeds with ruminate endosperm

Summary

The unitegmic, tenuinucellate ovules ofPsychotria andRandia show after fertilization a massive chalazal growth which is more pronounced in the former than in the latter. InPsychotria, the epidermis forms deep or shallow infoldings into the inner layers that grow around the young, quiescent endosperm; the infoldings are confined to the chalazal part alone and are absent in the integumentary part. InRandia malabarica, the epidermis forms shallow and irregular undulations both in the chalazal and the integumentary parts.

The endosperm remains quiescent and of small volume during the early stages of seed development. When the seed has attained nearly its mature size, the endosperm grows rapidly in volume and attains a ruminate configuration by replacing all the surrounding tissues of the seed except the epidermis which, with its infoldings or undulations, serves as the mature seed coat.Psychotria shows a graded variation from a pronounced degree of rumination inP. congesta to complete absence of rumination inP. bisulcata, through a gradually decreasing series represented byP. dalzellii, P. elongata, P. reevesii, P. serpens andP. macrocarpa. The cell walls of the mature seed coat do not become thickened inPsychotria, but inRandia malabarica, they acquire an Ericaceous type of lignification.