No. 464.] STUDIES ON PLANT CELL. VII. 569 



prothallus can so readily take on sporophytic potentialities and 

 the sporophyte develop gametophytes vegetatively. But Lang 

 recognized that the importance of this evidence woitkl be mini- 

 mized should it be found to depend on changes of nuclear struc- 

 ture. These nuclear changes have been established at least for 

 apogamy, either in the suppression of the reduction phenomena 

 of sporogenesis or by the substitution of asexual nuclear fusions 

 for the sexual act, and the argument for antithetic alternation 

 of generations seems to the writer stronger to-day than ever 

 before. 



6. APOSPORY. 



Apospory is the suppression of all processes of sporogenesis 

 and the development of a gametophyte generation directly from 

 the sporophyte. The term was first proposed by Vines (Jour, 

 of Bot., 1878, p. 355) in a discussion of the life history of Chara 

 and adopted by Bower ('86, '87) in a general treatment of the 

 subject based on Druery's ('86a, '86b) discoveries of prothalli 

 developed in place of sporangia directly upon the leaves of 

 Athyrium filix-fccmina and its variety clarissima. The phe- 

 nomenon of apospory is best known among the ferns where it 

 has been most extensively studied but so far no cytological inves- 

 tigations have been published. Since apospory results in the 

 development of a gametophyte generation (presumably with the 

 gametophyte number of chromosomes) without the preliminary 

 process of sporogenesis it becomes a very interesting problem to 

 know just how this reduction of the chromosomes is effected. 



Apospory is probably not uncommon in the mosses and has 

 also been reported for the liverwort Anthoceros. The inde- 

 pendent studies of Pringsheim ('76) and Stahl ('76) established 

 the facts that pieces of the sporophyte stalk (seta) of Hypnum, 

 Amblystegium, Bryum, and Ceratodon when placed on damp 

 soil developed a protonema which in its turn produced leafy moss 

 gametophytes. Stahl also found in Ceratodon that protonemata 

 may arise from the capsule wall and Brizi ('92) discovered a 

 similar development from the atrophied capsule of Funaria 

 hygrometrica. Correns ('99a, p. 421) has confirmed the conclu- 



