Spindle in Vegetable Cells of Higher Plants 455 



(Fig. 4). Whether this fact has any special significance can not 

 be stated at present. 



During the stage just mentioned, the chromatin thread is in 

 the form of the hollow spirem. The longitudinal splitting has 

 taken place earlier as described bv Mottier. In all the stages fol- 



lowing those represented in Fig. 1 until the separation of the 

 chromosomes at the equatorial plate this longitudinal splitting ex- 

 ists, but it is not shown in all the figures, for the process of stain- 

 ing necessary to bring out the spindle fibers clearly, leaves the 

 chromosomes too densely stained to enable one to distinguish the 

 daughter segments. 



The next important step in the process is the gradual disap- 

 pearance of the nuclear membrane. This appears first on the 

 sides next to the poles (Fig. 6). The kinoplasmic fibers enter the 

 nuclear cavity. Many attach themselves to the chromosomes 

 while others are seen to extend from pole to pole (Figs. 7, 8). 

 In Figs. 6, 7, 8, the poles of the spindle are broadly truncate, al- 

 though generally at this stage they are sharp pointed. The chro- 

 mosomes are somewhat crowded in the equatorial region but they 

 have not as yet become oriented into the equatorial plate of the 

 mature spindle. This behavior of the chromosomes during the dis ■• 

 appearance of the nuclear membrane and the penetration of the 

 spindle fibers into the nuclear cavity, is similar to that which has 

 been observed in pollen-mother cells (Mottier, '97). 



Fig. 1 1 is instructive in that several distinct poles are still pres- 

 ent in each polar region. The arrangement of the chromosomes 



in this fig 



the 



ment as Figs. 7 and 8. In the mature spindle here as in repro- 

 ductive cells, three sets of spindle fibers may be distinguished, 

 namely : those which extend from the poles to the chromosomes 

 to which they are fastened, those running from pole to pole, and 

 the so-called mantle fibers which diverge from the poles toward 

 the periphery of the cell in the equatorial region[(Figs. 8 and 11). 

 In the mature spindle the chromosomes are often quite regu- 

 larly arranged in the equatorial plate forming the well-known 

 monaster (Fig. 12). Frequently they do not appear to be ori- 

 ented with such regularity. At this stage the spindle is as a rule 

 strictly bipolar, but sometimes (Fig. 12) two or more poles still 

 persist. 



