MALE REPRODUCTIVE CELLS 



433 



d.m. 



appears is made up of a chromatic and an achromatic material, 

 mostly the latter. It is smooth and wiry, with darker masses at the 

 intersections of the strands 

 of the skein. 



Passing by several inter- 

 mediate stages, Figure 385 

 shows a more developed 

 cell in which it is to be 

 seen that the skein is much 

 broken up and its remains 

 have been gathered against 

 the nuclear membrane. 



These remains have also 

 either acquired the power 

 of staining, or they have 

 had other material added 



FlG. 386. Pollen mother cell of Magnolia with nu- 

 clear membrane gone, nucleolus very small, and chro- 

 mosomes forming. Achromatic fibrils are forming. 

 d.m., darker band of cytoplasmic material. X 1800. 



to them to take the stain. 

 This latter seems the more 

 probable when we notice 

 that during this time the large black-staining nucleolus has been going 

 through a process of disintegration by the formation of vacuoles. 

 While it appears larger on account of the vacuoles, it is undoubtedly 

 smaller in bulk. This has not been demonstrated by any measure- 

 ments, but is strongly indicated, if not proved, by the immediately im- 

 pending disappearance of the nucleolus by this same method. The 



chromatic matter is 

 thus gathered in irreg- 

 ular granules around 

 the periphery and these 

 granules increase in 

 size as the nucleolus 

 decreases in bulk. A 

 small portion of achro- 

 matic material re- 

 mains in a central 

 position. The whole 

 nucleus enlarges as 

 this proceeds. 



At the time at 



FlG. 387. Metaphase of first reduction division in Magnolia. -w}\\c}\ the nucleolus is 

 X 1800. 



dissolved, or shortly 



before, a series of achromatic fibrils appear in loose formation around 

 the edge of the nucleus whose wall becomes indistinct and disappears. 



