PLATE IV 



Fig. I. — Part of a univalent chromosome at first metaphase of 

 meiosis in Hyacinthus orientalis, pressed in fixation to show spiral 

 structure of two chromatids side by side. X 5000. (D., unpublished.) 



Figs. 2 and 3. — Chromosomes at first metaphase in Tradescantia 

 virginiana, fixed in boiling water and unstained, to show spiral structure. 

 (Sakamura, 1927.) x ca. 1000. 



Fig. 4. — First metaphase in Tradescantia rubra {^x = 24) pre- 

 treated with nitric acid, fixed in medium Flemming, stained in gentian- 

 violet. (La Cour, 1935. cf. Fig. 137.) X ca. 1800. 



