476 Woo levy. — Mdo tic Divisions in the Microspore 
and thickening of the threads to make a spireme of uniform thickness. 
Lawson ( 12 ) maintains that there is a shortening and thickening of the 
spireme threads, but he does not show the chromatin aggregated into a tight 
synaptic ball. It is difficult to say just what position the chromatin units 
take, if there are any which are truly such. The significance of any special 
arrangements which may occur is also difficult to determine. It is not until 
later stages that true splits are seen in the chromatin thread (Figs. 16 and 17). 
Figs. 11 and is show portions of thread which are much narrower than 
in most nuclei at this stage. Anthers from different flowers, however, show 
this difference in width of threads, especially noticeable at this stage. 
(Compare Figs. 9 and 10 with Figs. 11 and is.) 
Spireme. As the chromatin thread comes out of the synaptic state it 
is seen to have a greater diameter and is more uniform in thickness than the 
thread as it began to contract. This shortening and thickening has resulted 
in one continuous spireme. Sometimes the thread appears lumpy, but when 
it is evenly distributed throughout the nucleus, it appears as a smooth 
thread of uniform thickness (Fig. 14). Fig. 13 shows a slightly younger 
stage from a nucleus which was cut tangentially and was found in a loculus 
in which the nuclei all showed threads not yet fully untangled from the 
synaptic condition. The chromatin thread winds in and out through the 
nuclear cavity in a tortuous manner. 
There has been much discussion as to whether the nucleus at this stage 
contains one continuous chromatin thread or as many threads as the diploid 
number of chromosomes. Lawson (T1 a) identified individual chromosomes 
throughout all the prophases of the nuclei of Smilacina , while McAllister 
(T 3 ) finds a continuous spireme in Smilacina racemosa. This study shows 
the thread to be continuous, as has been found by McAllister (T 3 ), Mottier 
(' 07 , ’ 09 , T 4 ), and others. Several hundred nuclei were examined and 
studied under the best conditions to determine this point, and a model was 
made and sectioned to aid in the determination. Ends can be seen in 
abundance in sections of the nucleus showing spireme threads, but when 
it is possible to examine a whole nucleus or most of a whole one in one 
section the number of ends diminishes, so that it cannot be that there are 
as many threads as there are chromosomes appearing later. Fig. 14 shows 
almost a whole nucleus, and all the ends seen were carefully focused upon 
and appeared in such a plane that they surely were, at least most of them, 
cut ends. In Fig. 14 ten ends show, but this number is much too few if 
twenty-four is the haploid number of chromosomes for the plant. Long 
portions of continuous thread may also be traced through the nucleus. 
Loops appear to reach out to the nuclear membrane of some nuclei in 
the spireme stage, and some portions of thread run along close to the mem¬ 
brane for short distances, indicating that there are probably some con¬ 
nexions existing between the thread and the membrane. Such stages as 
