The phase change in ferns

Abstract

It is argued that the phasic alternation of sporophyte and gametophyte in ferns involves changing gene activation during oogenesis and sporogenesis respectively. The reasons for the change in activation are to be sought in the nutritional states of the cells in which the transition takes place. The readiness with Which apospory can the induced in ferns has enabled the features of meiosis which are essential for the switch in the form of growth to be distinguished from those which are related to the distinctive behaviour of the chromosomes. The dramatic changes in the cytoplasm of meiotic cells seem to have little morpihogenetic significance.