1908] YAMANOUCHI—APOUAUY IN NEPHRODIUM 303 



apparently by the cooperation of the mitoses of two different regions, 

 one of which is a single superficial cell that has attained a conspicuous 

 size, and the other the vegetative cells immediately beneath. If we 

 trace further back the origin of the cells of these regions, they are 

 found to be descendants from the vegetative cell or cells whose sister 

 cells have organized the cushion region. It was impossible to detect 

 a distinct period in which any change had occurred in the chromatin 

 condition up to this development of the sporophytic outgrowth; 

 practically the nucleus of the gametophyte has become directly the 

 nucleus of the sporophytic outgrowth, without any nuclear fusion. 



The sporophytic structure develops with repeated mitoses of the 

 same sort as was described before : a leaf and a stem apex are devel- 

 oped from two apical cells which have appeared one after the other; 

 a root initial is organized endogenously (fig. 29) ; scalariform vessels 

 appear in the tissue connecting the leaf and stem origins with the 

 root initial; and finally there is developed an independent leafy 

 sporophyte. 



From the foregoing it is clear that there is established a sporo- 

 phyte with the haploid or x number of chromosomes in Nephr odium 

 molle. This is the first instance yet known in plants, in which a 

 sporophyte with the haploid number of chromosomes has been 

 described. 



Whether the sporophyte thus formed may produce spores has 

 not yet been determined. 



Discussion of cytological phenomena 



APOGAMY 



Since the first discovery of apogamy in Pteris cretica, instances of 

 apogamy in pteridophytes have steadily increased until the phenome- 

 non is now known in about fifty forms. No cytological studies were 

 recorded until the appearance of the papers of Strasburger and of 

 Farmer and Digby, already cited, but there had appeared several 

 cytological studies of the apogamous development of the embryo in 

 spermatophytes. 



Apogamy (parthenogenesis and vegetative apogamy) is now 

 known in spermatophytes for Allium odorum (Tretjakow 69, Hegel- 

 maier 28), Balanophora (Treub 70, Lotsy 39), Antennaria alpina 



