Appendixes 3 1 7 



of the phenomena. If such a system of segrei^^ation is 

 actually formed at the apex, it must be supposed that the 

 axes of the system revolve with the generatino^ spiral. 



Whatever hypothesis be assumed, the following points 

 remain for consideration. 



1. We are as yet unable to imagine any simple system 

 by which the four original quadrants can be formed by 

 two similar divisions. Evidently there must be two cell- 

 divisions, and if in one of them we suppose AB to separate 

 from ab, we cannot then represent the formation of Ab and 

 aB. Therefore we are almost compelled to suppose that 

 the original zygotic cell forms two similar halves, each 

 AaBb, and that the next division passes differently through 

 each of these two halves, in the one half separating AB 

 from ab, and in the other half separating Ab from aB. The 

 formation of these four quadrants must take place in every 

 case in which there is segregation in respect of two pairs 

 of factors. (For three pairs there must similarly be eight 

 segments, and so on.) The axes of this system may well 

 be determined by the position of the constituent parental 

 gametes. Reduplication or proliferation resulting in n — i 

 gametes may then take place in either of the opposite pairs 

 of quadrants according to the parental composition. 



2. If in the gametes of any plant some factors are 

 distributed according to one of the reduplicated series and 

 other factors accordino^ to the normal Mendelian svstem — 

 as we know they may be — the segregations by which such 

 a system is brought about cannot have happened simulta- 

 neously. Moreover if various reduplications can take place 

 very early in some individuals and not in others, we cannot 

 imagine how the normal form of the plant remains un- 

 changed, unless these reduplications affect tissues originall)' 

 set apart as germinal. 



As possibly significant we note here the fact that in 

 the embryonic development of plants the order of the 

 various divisions is known to be subject to great variation 

 and it is not inconceivable that such disturbances of the 

 order in which the planes of division occur may indicate 

 variations in the process of segregation*. 



* See Coulter and Chamberlain, Morphology of Angiospcnns, 1903, 

 p. 187. 



