﻿276 BOTANICAL GAZETTE [ArRiL 



daughter segments and their orientation toward each other and 

 the manner in which the chromosome is fastened to the spindle. 



In Lilium the daughter segments are, as a rule, rather long 

 rods closely applied to and twisted upon each other. As shown 

 in the preceding pages, there are many variations from the usual 

 form. They are generally fastened to the spindle fibers at the 

 end, and under such circumstances placed radially upon the 

 spindle. 



During metakinesis, the second longitudinal fission manifests 

 itself, and each daughter chromosome consists of two grand- 

 davighter segments, which usually adhere and sometimes fuse at 

 the ends to which the spindle fibers are fastened, while the 

 opposite ends may diverge to form the V- or U-shaped figures. 

 It often happens that the free ends of the granddaughter seg- 

 ments do not diverge, in which case the retreating daughter 

 chromosome is in the form of two contiguous or nearly contigu- 

 ous rods. Sometimes the ends of the granddaughter segments 

 appear so completely fused near the place of fastening to the 

 spindle that the daughter chromosome resembles a continuous 

 rod bent into the^shape of a V or U. On the other hand, V- and 

 U-shaped daughter chromosomes are brought about by another 

 process, namely, that of a bending. Under this circumstance 

 the chromosomes are attached to the spindle, not by the ends, 

 but near the middle or at some distance from one end, and the 

 orientation upon the spindle is generally tangential. The V- or 

 U-form is then due either to a previous bending of each daughter 

 segment in such a manner as to form a ring or loop, or the bend- 

 ing may be caused by a pushing or pulling of the spindle fibers 

 during the meta- or anaphase. In all such cases the V's or U's 

 so formed are double as a result of the second longitudinal 

 splitting. 



The fact that in many plants the daughter nucleus passes into 

 the resting stage would seem to indicate that the second or 

 homotypic mitosis signifies something more than the mere dis- 

 tribution of the granddaughter chromosomes to the grand- 

 daughter nuclei. In such cases it is difficult to understand the 

 purpose of two longitudinal fissions during the first karyokinesis. 



