No. 464.] STUDIES ON PLANT CELL.— VII. 571 



generally appreciated and the studies on apospory and apogamy 

 indicate that much of it is associated with these fundamental 

 modifications of the life history (Druery, :oi). 



As to the cause of apospory we are as much in the dark as in 

 the case of apogamy. The phenomenon is clearly associated in 

 some forms with disturbances in the normal vegetative life of 

 the sporophytes. This is particularly true in the cases of mosses 

 and Anthoceros and has been suggested for the ferns. Thus 

 aposporous developments in Pteris aquilina are from leaves which 

 are generally smaller than the normal and whose margins are 

 curled so that the leaf often appears somewhat withered and is 

 easily recognized at a distance. Bower ('87, p. 322) is inclined 

 to regard the phenomenon in the ferns as a sport and does not 

 consider that it has deep morphological significance or that it 

 offers serious difficulty to the acceptance of the theory of an 

 antithetic alternation of generations. 



As we have stated there have been no cytological studies upon 

 apospory but there seem to be two possible explanations. That 

 which is likely to suggest itself first calls for reduction phenom- 

 ena at the time of the aposporous development by which the nuclei 

 of the sporophytic tissues may come to contain the gametophyte 

 number of chromosomes and are therefore capable of developing 

 the sexual generation. But there is another possibility which 

 has not yet been considered. We know for several of the sper- 

 matophytes (Antennaria, Juel, : 00 ; Thalictrum, Overton, : 04 ; 

 Alchemilla, Strasburger, : 04c) that the processes of sporogenesis 

 may be suppressed and yet a structure be developed with the 

 morphology of the gametophyte generation. Thus the embryo- 

 sac will contain the usual number of nuclei grouped in the typ- 

 ical manner but these nuclei still have the sporophyte count of 

 chromosomes. It seems probable then that the development of 

 a gametophyte may result through an interference with the nor- 

 mal life history and under conditions favorable to the game- 

 tophyte even though the nuclei retain the sporophyte number 

 of chromosomes. And it is possible that some of the aposporous 

 developments in bryophytes and pteridophytes may be of this 

 character. It is quite futile at present to carry this speculation 

 further. What is desired is some cytological facts. 



