368 BOTANICAL GAZETTE [November 



of the nucleus. Some investigators, however, do not regard it in 

 this light. For example, Lawson 2 makes the following statement. 



During their development, however, there is a great accumulation of sap 

 within the nuclear cavity, which causes a great osmotic pressure. The pressure, 

 acting from within, causes the nuclear cavity to expand. This expansion con- 

 tinues until the nuclear cavity grows to twice or even three times the original 

 size. As the growth proceeds the membrane is gradually withdrawn from the 

 chromatin mass within. The result of this withdrawal of the nuclear membrane 

 is the formation of a large clear area of nuclear sap containing the mass of 

 chromatin which has been left at one side. No evidence whatever was found 

 to show that any contraction of the chromatin had taken place. 



In my material of D. Kaki I could not recognize such a remark- 

 able enlargement after the chromatin reticulum began to separate 

 from the nuclear membrane. The great enlargement of the nucleus 

 occurs in the resting stage, so that there is no conspicuous differ- 

 ence in the size of the nucleus at the synapsis stage and at the end 

 of the resting stage, as Lawson indicates. 



The synapsis stage is a normal occurrence, and during it there 

 is some rearrangement, but not fusion of chromatin bodies, which 

 results in the spireme stage. At the beginning of the spireme 

 stage the thread is distributed in the outer cavity of the nucleus, 

 where thickening and shortening occur, resulting in the diakinesis 

 stage (pi. figs. 6, 7, 8). There is no difference in the size of the 

 pairing chromosomes, which are usually parallel, but sometimes 

 X or V-shaped. At the same time there appear in the cytoplasm 

 numerous fibers which penetrate the nuclear cavity and become 

 attached to the chromosomes by one end, in connection with 

 which the nuclear membrane begins to disappear. By the elonga- 

 tion of the fibers the chromosomes, which have been distributed on 

 the surface of the nucleus, are drawn into the center of the nuclear 

 cavity, and there are arranged in an equatorial plate by the gather- 

 ing of the free ends of the fibers at the poles (pi. figs. 9, 10, n). 

 The nucleolus disappears entirely during metaphase. 



The number of chromosomes is difficult to count by reason of 

 their small size. Usually there are 28 in pairs, but sometimes 



2 Lawson,-A. A., The phase of the nucleus known as synapsis. Trans. Roy. Soc. 

 Edinburgh 47:591-604. ph. 2. 1911. 



