



Figure 6-3. Electron Micrographs Showing Spindle Fibers in (a) Pollen 

 Mother Cell of Lilium speciosnm at Metaphase I, and (b) Meristematic Cell 

 of Pisiim Root Tip at Somatic Anaphase. (Fig. (a), from Sato, S., 1960. 

 "Electron Microscope Studies on the Mitotic Figure. III. Process of the 

 Spindle Formation," Cytologic!, 25, Fig. 8, p. 126. Courtesy of Dr. S. Sato, 

 University of Tokyo. Fig. (b), courtesy of Mr. L. V. Leak, Michigan State 

 University.) 



Every physical and physiochemical force which could conceivably 

 bring about movement of the type exhibited by chromosomes in mitosis 

 has been invoked in attempts to explain the mechanism. Most of these 

 are discussed in detail in Franz Schrader's book, Mitosis (1953), and 

 will be mentioned here only briefly. 



Elastic Fibers 

 This is perhaps the oldest idea of all, and many variants of the basic 

 scheme have been proposed. Fundamentally the notion is that the 



MECHANICS AND PHYSIOLOGY OF CELL DIVISION / 143 



