Morphogenesis in Marsilea

An account is given of investigations on the development of sporelings of Marsilea using aseptic culture techniques. Special attention was paid to the heteroblastic leaf development and to the conditions leading to the origin of land or water forms. A study was made of the effects of changes in the composition and concentration of the culture medium. The substances tested included sugars, nitrogen compounds, metabolic inhibitors, auxins, gibberellic acid and kinetin. It was concluded that the changes in leaf segmentation of Marsilea, or heteroplastic development, are correlated with changes in the size of the apical meristematic regions of the shoot, which in turn are influenced by the nutritional status of the plant. On the other hand, the differences between land and water forms are probably due to differences in the available concentration of dissolved carbohydrates in the growing parts. The results are discussed in relation to similar morphogenetic problems in other vascular plants.