Bui. 844, U. S. Dept. of Agriculture. 



Plate 



Development of the Ovules and Pollen in Sweet Clover. 



Fig. 1. — Section through the nucellus of an ovule of Melilotus alba, showing two megaspore mother cells. 

 X360. Fig. 2. — Median section through an ovule of Melilotus alba, showing the two cells resulting 

 from the first division of the megaspore mother cell, and the relative development of the different 

 parts of the ovule. X300. Fig. 3. — Section through the nucellus of an ovule of Melilotus alba , show- 

 ing two embryo sacs, one being more advanced than the other. X360. Fig. 4.— Protoplasm of the 

 pollen mother cell of Melilotus alba contracted and ready to undergo division. X 560. Fig. 5. — Pollen 

 grains of Melilotus alba just formed , showing their dense cytoplasm and the presence of the mother- 

 cell wall. X560. Fig. 6.— a, Mature pollen grain of Melilotus alba, showing the binucleate condition 

 at the time of shedding; b, surface view. X560. 



