MITOSIS IN POLLEN MOTHER-CELLS. 23 



THE TELOPHASE. 



As soon as the daughter chromosomes arrive at the poles, they 

 approach each other very closely, so that, in many cases, the separate 

 individuals cannot be recognized. But very frequently the segments 

 do not become so closely crowded together, and the manner in which 

 the daughter spirem is formed can be followed with accuracy. The 

 formation of the spirem can best be observed when the granddaughter 

 segments arrive at the poles in the form of the familiar V-shaped 

 figures. Generally the ends forming the angles of the V fuse first, 

 unless this has already been accomplished ; then the free ends meet end 

 to end and unite (Fig. 10, G). In this way there is formed a continuous 

 single spirem in which the identity of the individual segments or 

 granddaughter chromosomes is lost. 



If all the daughter chromosomes were regularly V- or U-shaped the 

 spirem would be regular, consisting of an orderly series of nearly 

 uniform turns ; but the spirem rarely shows such regularity, because 

 the chromosomes vary in size and shape and in the manner in which 

 the granddaughter segments are oriented with respect to each other 

 in the several pairs. During the reconstruction of the daughter 

 nucleus, the chromosomes tend to reticulate, that is, to become 

 irregular and lumpy, so that an irregular skein or net results. This 

 is less pronounced in Lilium than in many other plants. 



The fact that pairs of granddaughter segments arrive at the poles in 

 different forms, such as V's, double U's, and pairs of parallel rods, 

 shows clearly that in such cases the resulting spirem must be very irreg- 

 ular. The chromosomes are generally so closely crowded together 

 that it is not possible to determine with certainty just how the variously 

 shaped pairs of segments behave. But it is reasonable to suppose that 

 the segments of the double U's and those of contiguous rods must first 

 separate in order to unite end to end, for no case has been clearly made 

 out in Lilium in which a part of the spirem is formed double. 



The newly formed daughter spirem is close with relatively short 

 turns (Fig. 10, G, H). Between each tw extends the beautiful system 

 of connecting fibers, which represents the central fibers of the spindle. 

 Fibers are also present which extend from each spirem toward the 

 plasma membrane in the direction of the equator. Some of these 

 reach the plasma membrane, while others seem to end blindly in the 

 cytoplasm, or pass over into its thread-work. In Lilium there are no 

 polar radiations. 



The system of connecting fibers soon becomes barrel-shaped, and 

 the cell-plate makes its appearance in the equatorial region. We 

 shall return to the formation of the cell-plate beyond. 



