The Interrelation of Meiosis and Mitosis: I. The Mechanism of Agamospermy

A CCORDING to the terminology introduced by EDMAN (1931) and r t i n similar fashion by STEBBINS and JENKINS (1939, in the press), agamospermy comprises the phenomena of diplospory, apospory and nucellar embryony.In the first two cases a gametophyte is formed, in the third case a sporophyte arises directly from the mother sporophyte.Diplospory is the formation of a gametophyte from archesporial cells and their descendants and consists of diploparthenogenesis and apogamety, dependent on the formation of an embryo from an egg-cell or from another gametophytal cell.Apospory is the formation of a gametophyte from extra-archesporial tissue.If the egg-cell in the aposporous embryo-sac can develop, this development implies parthenogenesis as in the case of diplospory.Accordingly, diplospory, as well as apospory, can be followed by parthenogenesis (and -or -apogamety).Instead of the term diplospory, STEBBINS and JENKINS use the expression generative non-reduction.The following scheme may visualize the terms mentioned: Diplospory 1) (Diplo-] parthenogenesis 2) Apogamety A.gamospermy. Apospory 1) Parthenogenesis 2) Apogamety Nucellar embryonyFollowing ERNST (1918) but contrary to ROSENBERG (1930), the author regards apospory and nucellar embryony as closely related phenomena, the development of nucellar embryos being not only a case of vegetative propagation (ROSENBERG, 1930, p. 43).Nucellar embryony is a special case of apospory where the aposporous embryosac has been reduced, being only unicellular.This opinion was also held by TXCKHOLM (1922), who introduced the term agamospermy as a 16015223, 1939, 3,