﻿456 



BOTANICAL GAZETTE 



[JUNE 



each chromosome having a ladder-like appearance (figs. 2-8). 

 The rate of vacuolization is by no means uniform, as will be seen 

 from an examination of figs. 2-5, and the distribution of chromatin 

 over the ladder thread is very uneven, being heavier at the junction 

 of the sides and the connecting strands. During this process 

 several nucleoli appear in the comparatively large open spaces of 

 the nucleus, each large nucleolus containing a relatively . large 

 oblong vacuole (figs. 5, 8). 



It must be kept in mind that the ladder structures with their 

 two sides and connecting strands have arisen from single somatic 

 chromosomes, and are the result of a series of vacuoles along their 

 median longitudinal axis. The so-called typical resting stage 

 consists entirely of these structures, therefore, still joined more or 

 less with one another by the anastomoses that arose at the last 

 telophase (figs. 5-8). In the very early prophase the sides of the 

 ladder are very fine (figs. 3, 4), but as the chromatin material in- 

 creases, the threads become heavier and more uniform (figs. 5-8), 

 while at the same time the anastomoses break down, and the 

 connecting strands of chromatin between the two parallel sides 

 grow finer and finer (figs. 7, 8) until they entirely disappear, leaving 

 as a result two, parallel threads (fig. 8), which are daughter halves 

 of single somatic chromosomes. 



As the parallel spirems, now entering synapsis, contract and 

 condense, they gradually approach each other and approximate, 

 at times twisting about one another (fig. 9) and resulting in a single 

 thick spirem (figs. 10-13) which is the condition of complete 

 synapsis, the heavy thread appearing as a homogeneous structure 

 twisted and coiled about itself (figs. 11, 12), causing the mass to 

 have a lumpy, granular appearance (fig. 12). At no time during 

 this period, when sectioning and staining have been the best, is the 

 thread lost to view (figs. 9-14) ; for even at the time of the greatest 

 contraction, portions of the thread may be traced across the mass 

 (fig. 11). This step in development is not necessarily uniform, 

 for portions of the spirem in synapsis have been observed showing 

 the double nature distinctly (fig. 10). 



While these activities are going on, the nuclear cavity as well 

 as the entire cell enlarges; although most of the growth is after the 



