22 



BOTANY 



PART 



usually lies in the future plane of division of the cell. It is seen in 

 surface view in Fig. 14. 



While the nuclear network is separating into the individual 

 chromosomes, cytoplasmic filaments become applied to the nuclear 

 membrane, surrounding it with a fibrous layer. This layer becomes 

 raised up from the nuclear membrane at two opposite points 

 (6 Jc) and forms the polar caps. The filaments converge at the poles, 



FIG. 13. Successive stages of nuclear and cell division in a meristematic cell of a higher plant. 

 Somewhat diagrammatic. Based on the root of Najas marina, fixed with the chrom-osmium- 

 acetic mixture and stained with iron haematoxylin. n, Nucleus ; nl, nucleolus ; w, nuclear 

 membrane ; ch, chromosomes ; k, polar caps ; s, spindle ; kp, nuclear plate ; t, daughter nucleus ; 

 v, connecting fibres ; z, cell-plate ; m, new partition wall. The chromatophores are not visible 

 with'this fixation and staining. ( x about 1000. After CLEMENS MOLLER.) 



where they constitute two pointed bundles. At this stage the nucleoli 

 (nl) are dissolved and the nuclear membrane disappears. The fibres 

 proceeding from the polar caps can thus become prolonged into the 

 nuclear cavity (7). Here they either become attached to the chromo- 

 somes, or filaments from the two poles may come into contact and 

 extend continuously from the one pole to the other. In this way the 

 nuclear spindle (7 5) is formed. The two halves of each chromosome 

 separated by the longitudinal split now separate in opposite directions 



