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Practical Plant Biology. 



the usual nuclear dyes, the achromatic spindle. The chromo- 

 somes appear each associated with a single spindle-fibre, one 

 limb directed towards one of the poles, while the other lies ap- 

 proximately in the equatorial plane extended towards the periph- 

 ery. At the same time stained specimens often show striae of 

 cytoplasm similar to the fibres of the achromatic spindle, radiating 

 from the poles into the general granular cytoplasm of the cell. 

 It is possible that the fibres of the achromatic spindle are produced 

 in the killing and fixing of the protoplasm, being formed as a 



i k 



FIG. go. Lilium martagon, somatic mitosis, x 700. a, nuclear thread 

 formed from net-work ; b, nuclear thread shortened and thickened ; 

 c, formation of chromosomes ; d, equatorial (nuclear) plate of chromo- 

 somes ; e, longitudinal cleavage of chromosomes ; /, beginning of the 

 separation of the half chromosomes ; g, parting of the halves ; A, move- 

 ment of the halves towards the poles; i, congregation round the poles; 

 k, formation of the new nuclei from the halves and appearance of the 

 cell-plate across the middle of the achromatic spindle. 



coagulation product between the colloids of the central protoplasm 

 and the reagents used. This surmise is rendered more probable 

 by the fact that similar structures may be produced in egg-white 

 with the usual fixing reagents. 



The next change observable is the splitting of each chromosome 

 longitudinally. In suitably stained specimens it may be seen that 

 this cleavage is the result of the division of each of the minute 

 chromomeres of the thread. The two parallel linear series formed 

 by this division constitute the halves of the chromosomes. These 



