Floral histogenesis in the Monocotyledons. II. The Cyperaceae

Abstract

An account is presented of floral histogenesis in Scirpus validus Vahl, Cyperus eragrostis Lam., and Carex appressa R. Br. The cells of the apex of the spikelet in the three species are arranged in a two-layered tunica over a central corpus. Histogenetically the outer and inner tunica layers behave differently and are termed dermatogen and hypodermis respectively. The same three tissue zones are recognized in the flower primordia. Periclinal division of dermatogen and hypodermal cells gives rise to (i) the glumes or floral bracts and carpels in all species, (ii) the perianth members in Scirpus, and (iii) the perigynium in Carex. These are all classified as foliar organs. Periclinal divisions in cells of the outer corpus layers, and inclined and periclinal divisions in the hypodermis, characterize the formation of flower and stamen primordia. Periclinal division of dermatogen cells never occurs. These organs are regarded as cauline. The ovule develops directly from the growing point of the flower primordium and its integuments arise in the foliar fashion. The general pattern of histogenesis is compared with that in the Gramineae. Variations within this pattern and the interpretation of the floral structures are discussed.