82 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 31) Ser. 



EXPLANATION OF PLATE XIIL 



Fig. 20. The daughter nuclei are formed. They are at this time crescent 

 shaped as seen in section. There is still a shell of granular mat- 

 ter bounding the remains of the spindle. It is seen in section as 

 two lines. 



Fig. 21. The daughter nuclei have become spherical. The granular matter 

 has increased in quantity. 



Fig. 22, A spindle of the second division. The other spindle, whose posi- 

 tion is indicated by the circular mass of granular matter, lies at 

 right angles to the first. 



Fig. 23. Two spindles of the second division that lie nearly parallel to each 

 other. The granular mass between them is not of equal density 

 throughout. 



Fig. 24. The four daughter nuclei, each surrounded by a dense granular 

 zone. They are connected by mantle fibers. 



Fig, 25. A young pollen-grain. The nucleus is surrounded by a dense gran- 

 ular zone and the cytoplasm outside of this contains much gran- 

 ular matter. 



