Anatomy of Ricciocarpus natans, with emphasis on fine structure

Abstract

The amphibious liverwort Ricciocarpus natans has been investigated with regard to structure and differentiation of cells and tissues.The differentiation of the tissues was determined starting with their origin from the meristem situated in the median furrow. From this zone there is dorsally a differentiation of epidermis and aerenchyma, and ventrally a differentiation of epidermis and scales. Air–chambers arise schizogenously. They become divided by cells, which grow out from lateral walls and form an internal pore.Parenchyma (aerenchyma and euparenchyma) cells and epidermis cells (including thallus margin and main scale cells) appear similar in ultrastructure. A characteristic localization of heteropycnotic chromatin close to the nucleolus is recognized. Mic–robodies have an extraordinary cap–shape. Vacuoles often contain electron dense bodies. Lipid droplets occur frequently in the cytoplasm. Storage products are not restricted to a certain tissue. Young scales have an apical papilla cell with many dictyosomes. Chloroplasts of the oilbody idioblast are much smaller than those of unspecialized cells. The rhizoids are smooth–walled.