iqo8] YAMANOUCHI— APOGAMY IN NEPHRODIUM 291 



conclusion than that the normal life-history is checked at a critical 

 period (fertilization) and that the plant is forced into an expression 

 of vegetative activity. Apogamy brings forward also the theory of 

 the homologous origin of alternation as contrasted with the antithetic. 

 The theory of the homologous origin of the alternation of generations, 

 as held by Pringsheim (55,56) and Scott (61), is discussed by 

 Lang in his studies on apogamy. He is inclined to the opinion that 

 apogamy and apospory in ferns support the homologous view, since 

 the prothallium can so readily take on sporophytic characters and 

 the sporophyte can develop the gametophyte aposporously. He 

 recognized, however, that all speculations on these points must be 

 tentative until the actual nuclear conditions in apogamy and apospory 

 have been ascertained. 



The investigations mentioned above have greatly extended our 

 knowledge concerning the phenomena of apogamy and apospory, and 

 some of them have contributed much to elucidate the structural 

 features involved, but cytological details of apogamy in pteridophytes 

 remained unknown until last year, when there appeared two papers, 

 one by Farmer and Digby (24) and the other by Strasburger (68). 



Farmer and Digby's paper is one of the most important of recent 

 contributions to apogamy in ferns. Their preliminary note (23), 

 published four years ago, announced the discovery of nuclear fusions 

 in the vegetative cells previous to the apogamous sporophytic out- 

 growths from prothallia. The final paper deals with the results of 

 their studies on apogamy and apospory in the following seven forms: 

 Lastrea pseudo-mas vars. polydactyla Wills., polydactyla Dadds, 

 cristata apospora Druery; Athyrium Filix-joemina vars. clarissima 

 Jones, clarissima Bolton, and unco-glomeratum Stansfield; and 

 Scolopcndrium vulgare var. crispum Driimmondae. 



All the prothallia of the five forms used for their investigations, 

 excepting the two polydactyla varieties, were aposporus outgrowths, 

 either on peripheral cells of unmatured sporangia, from sori of sterile 

 sporangia, or on apices, surface, or margins of pinnae. In two forms 

 — var. unco-glomeratum and var. cristata apospora — the aposporous 

 prothallia were induced artificially by pegging detached pinnae down 

 on damp soil. The two varieties polydactyla of Lastrea, producing 

 ordinary spores and prothallia, were obtained by sowing the spores. 



