PLATE LII. 



Fig. 4. — Median longitudinal section through a bud, showing the 

 formation of the "glockenkern" at the apex. Stage C. 



Fig. 5. — Median longitudinal section through a bud, showing germ 

 cells migrating into the pear-shaped "glockenkern." Stage D. 



Fig. 6. — Median longitudinal section through a bud, showing the sepa- 

 ration of the two layers of the "glockenkern" cell mass and the formation 

 of the manubrium. Stage E. 



