Morphogenesis of the frond of Gracilaria verrucosa (Huds.) Papenfuss: the differentiation of vegetative and sexual areas

Abstract

Recently, we (Kling & Bodard, 1986) described the morphogenesis of the vegetative thallus of Gracilaria verrucosa and compared this development with that of other algae and higher plants (cormophytes). The development of the thallus is based on a series of jointed cladomes terminated by apical cells designated A₁, A₂, A₃… A_n. We have not demonstrated the existence of lateral “pleuridie” cells (Kling & Bodard, 1986). The thallus that comes from the successive division of this series of apical cells, evolves both the cortex and the medullar cells. The originality of this construction lies in the continuous formation of apical cells which are further being separated into subapical or segment cells SA₁, SA₂, SA₃… SA_n. These cells are formed only secondarily.