i^4 



c 







i? *^C^*^ 



^ ^^^ 



Plate 5. — The Spiral Structure of Chromosomes. 



nd B. Meiotic metaphases in pollen mother cells of Trillium erectum. 



(From Huskins and Smith) 



Meiotic metaphase in Fritillaria sp. (Courtesy of C. D. Darlington) 



