116 Allow Burdette Stout 



Plerome. periblem and dermatogen, and calyptrogen are sharply- 

 delimited in the roots of Carex aquatilis and the lines of demarcation 

 are even carried through the embryonic apex of the root. The resting 

 nuclei of all these regions show the structure described above. I have 

 drawn a group of cells from the center of the embryonic region to show 

 this (fig. 4). Cells a and b belong to the plerome, c and d to the periblem 

 and dermatogen, and e is a cell of the calyptrogen. These are typical 

 resting cells of the embryonic region. 



That the chromatin masses which are present in these nuclei are 

 the individual chromosomes is evident from a study of their subsequent 

 history and appearance in the division figures. In shape they are some- 

 what irregular but compact masses entirely similar to the chromosomes 

 as they appear in the middle prophases of the somatic divisions. In 

 careful counts in a large number of resting nuclei I have in no case found 

 more of these masses than the number of diploid chromosomes. The 

 number established by counts of the equatorial plates of somatic, hetero- 

 typic, and homoeotypic division figures is, as near as I can determine, 

 seventy-four. The chromatin units in the resting nuclei are small and 

 often two or three of them are more or less massed together or overlie 

 each other so that it is not possible to count them with complete cer- 

 tainly. It is clear, however, that their number does not exceed that 

 of the chromosomes appearing in the equatorial plate. 



The preparation shown in figure 4 is characteristic in this particular. 

 The entire nucleus of cell c is present in the section and in it nearly se- 

 venty individual chromatin bodies are visible. Parts of the other nuclei 

 drawn did not show in the section. Of the nuclei & and e about one-half 

 is shown and forty-two chromatin units appear. Larger portions of the 

 nuclei a and d are shown with a proportionally greater number of chro- 

 matin masses. 



As noted above, a most conspicuous and interesting feature of the 

 resting nuclei is the arrangement of the chromatin masses in series. It 

 is not entirely clear that there is a single continuous spirem at this stage, 

 but as is clearly shown in the drawing, in various regions of a nucleus 

 a series can be traced for some distance. Where two series cross or are 

 massed together it is difficult to trace the line. Cross fibres from one 

 series to another may be present, but they are secondary. In these rest- 

 ing nuclei the chromosomes are definite bead-shaped bodies connected 

 by rather thin strands of linin. When closely placed the series is easily 

 traced; where the individuals are farther apart the connecting linin 

 strands are followed with more difficulty. 



