120 Arlow Burdette Stout 



loosely aggregated and the individuals can often be distinguished. There 

 is considerable variation in the degree of development attained by the 

 spindle fibres and polar rays. Figure 16 shows a well developed figure 

 with rather unusually heavy astral rays; figure 17 is a somewhat later 

 stage of a more weakly developed spindle figure. 



The nuclear membrane now forms about the whole group of daughter 

 chromosomes while they are massed together. The daughter nucleus 

 so formed enlarges and the mass loosens up somewhat, the chromosomes 

 become separated, and it is seen that they lie against the membrane 

 and are connected in series as shown in figures 18 and 5 a. For a time 

 various chromosomes remain massed together as is seen in figure 18. 



One or more nucleoles appear simultaneously with the formation 

 of the membrane. The nucleus continues to increase in size, the chromo- 

 somes become more widely distributed until the condition of the resting 

 nucleus is again reached. Meanwhile the cell-plate forms from the cen- 

 tral spindle fibres after which the fibrous system disappears and the 

 cytoplasm passes into a finely reticulated and vacuolated condition. 



Following the telophases there seems to be but little growth in the 

 volume of the individual chromosomes. As one observes the resting 

 nuclei he is impressed with the apparently small amount of chromatin 

 compared with that present in the division stages. This is partly due 

 to the scattered position of the chromosomes because of which only a 

 part of them appear in a single optical section. They are, however, much 

 smaller during the resting stages. Their visible increase in size is a pre- 

 paration for division. 



The characteristic features of the cell division in the root tips of 

 Carex may be summarized as follows: 



1. The chromosomes are individualized bodies which can be iden- 

 tified not only at every stage in the division, but in resting nuclei as well. 



2. They also maintain a serial arrangement which gives them a 

 definite position relative to each other. This arrangement in a discrete 

 spirem is in evidence in resting nuclei, but is most conspicuous in the 

 prophases. 



3. The chromosomes also pass into the equatorial plate in the same 

 serial order they had in the prophases and this order is probably main- 

 tained through the anaphases. 



The nuclei in the cortex and in the central cylinder further back 

 in the root where division has ceased also show the chromosomes as de- 

 finitely individualized bodies. Figure 1 shows this feature in typical 

 nuclei in elongated cells of the central cylinder. 



