RICHARDS: MITOSIS IN PODOPHYLLUM. 91 



termine, however, that such was not the case, and it seems quite 

 certain that the spindle is formed without the influence of 

 other archoplasmic structures. 



In most cells there is no metaphase for the entire chromo- 

 some mass, ?'. e., an equatorial plate, in these cells, but each 

 chromosome passes through the stage without waiting for the 

 others. Figures 7 and 11 are the only approach to such a con- 

 dition, and even here there is some lack of uniformity in the 

 division of the chromosomes. Figures 8, 9 and 10 show the 

 usual condition of the equatorial plate. Figure 10 shows the 

 longitudinal split of the undivided chromosomes very clearly. 

 This cell was crushed, but the crushing served to bring out the 

 split all the better. 



During the metaphase the first signs are seen of the concen- 

 tration of the cytoplasm at the center of the cell, where the 

 new wall is to be formed, and the consequent vacuolation of the 

 cytoplasm at the poles. (This phenomenon is the usual occur- 

 rence in these cells but there are numerous instances where it 

 is only slightly marked.) This concentration seems to aid in 

 the construction of the new cell plate, for the more marked the 

 concentration the more rapid the cell-plate formation. 



In regard to the division of the chromosomes nothing un- 

 usual was observed. The chromosomes divide and pass to the 

 poles as in most forms. In passing up to the poles the chromo- 

 somes usually turn with the short arm of the J toward the cen- 

 ter of the spindle. One chromosome seemed to stand out from 

 the rest slightly and was especially marked by its size ; this was 

 the long chromosome m (figs. 9, 14). Polar views of the ana- 

 phase present the best opportunities for counting the chromo- 

 somes, but there is much uncertainty even here, owing to the 

 diflficulty of getting all of the plate in one section or of tracing 

 it through neighboring sections. Fourteen chromosomes were 

 counted in about a dozen cells, but this, of course, is insuffi- 

 cient evidence on which to base a decision. 



Arrived at the poles the chromosomes fuse end to end and 

 then form a loose daughter "skein." This "skein" becomes a 

 close one and the chromatin forms a dense mass at the poles. 

 The remainder of the nuclear reconstruction consists in the 

 formation of the membrane, the distribution of the chromatin 

 granules in the nuclei, the appearance of the linin network and 

 the formation of new nucleoli. It is a general rule that the 

 nucleoli arise on the side of the cell nearest the new cell wall. 



