﻿4 ;c 



BOTANICAL GAZETTE 



the spirem is a single structure splitting during the spirem stage 

 demonstrate that the separation during anaphase is the result of 

 this former activity. 



Contrary to most reports, the halves of the chromosomes in 

 Allium tricoccum become entirely dissociated during anaphase, so 

 that a polar view of such shows 16 individuals, or the 2X number. 

 These 16 remain distinct from now on, and at late anaphase or 

 early telophase they join up end to end (fig. 38), after which the 

 looping spirem becomes very much crowded. As some karyo- 

 lymph still remains, this diffuses out and the nuclear membrane 

 is formed about the densely crowded chromatin mass, as described 

 by Lawson (20) and Yamanouchi (32). 



HOMOTYPIC MITOSIS 



A spirem consisting of 16 segments, that approximated end 

 to end at late anaphase of the previous mitosis (fig. 38), forms early 

 in the daughter nucleus (fig. 42), since a resting condition does not 

 intervene. In all reports read concerning the homotypic divisions, 

 the spirem is interpreted as being x chromosomes in length and 

 double, owing to the longitudinal separation during the previous 

 anaphase. As the multipolar spindle appears, the spirem forms 

 16 segments (fig. 44) which immediately pair (fig. 45), forming 

 8 pairs of half chromosomes. It is probably owing to the rapidity 

 of the pairing that previous investigators have claimed the longi- 

 tudinal split to be completed at this time instead of during the 

 heterotypic mitosis. Unless a close series had been followed and 

 the end to end approximation of the half chromosomes been 

 observed, the author would probably have made a similar inter- 

 pretation. If each chromosome is to maintain its individuality, 

 no other results could be expected. 



All this goes to show that at metaphase of heterotypic division 

 there is a reduction or separation of characters, but it is not until 

 homotypic division that the reduction in number is actually 

 accomplished. 



Conclusion 



In comparing the nuclei during the reduction division, as seen 

 in Allium tricoccum, with the nuclei during somatic division, as 

 described by Sharp (28) for Vicia Faba root tips, it is seen that 



