(a) 



% 



^ 



(b) 



Figure 4-8. (a) Photomicrograph of Nucleolus in Microspore Cell of Tra- 

 descantia. (b) Nucleolar Chromosomes as Seen at Diakinesis of Meiosis 

 in Spinacia olerocea L. Two pairs of chromosomes are associated with each 

 nucleolus. (Fig. (a), courtesy of Mr. L. V. Leak, Michigan State University, 

 E. Lansing, Michigan. Fig. (b) from Bemis, W. P. and Wilson, G. B., 1953. 

 "A New Hypothesis Explaining the Genetics of Sex Determination in 

 Spinacia oleracea L.," J. Heredity, 44, Fig. IC, p. 90.) 



82 / CHAPTER 4 



