Marsilea vestita: Conversion of the Water Form to the Land Form by Darkness and by Far-Red Light

A period in darkness or in continuous far-red light can cause the ferns of the species Marsilea vestita Hook. and Grev. to develop as a land form in a medium which normally allows only the water form to develop. Far-red light is more effective than darkness in causing this conversion. The difference in the quality of light reaching plants growing in water or on land may cause this conversion to occur in nature.