246 Univcrsit}/ of California Publications in Agricultural Sciences [Vol. 2 



regions. The barrel-shaped spindle would hold tlieni in ring formation. 

 When the nuclei have attained their final size, the plastids, now filled 

 with starch, form two rows with the cell plate between them. With the 

 formation of the second spindles this line of division is obliterated. 

 It is possible either that the processes involved in cell plate formation 

 produce the line of division, or that it results from the action of the 

 opposing forces concerned in chromosome division. In any case, the 

 distortion of the ring at late second ana- and early telophase might 

 result from the pull of the same forces which separated the chromo- 

 somes. The final division of the plastids into four groups may depend 

 somewhat upon the invaginations which give rise to the lateral walls 

 of the pollen case. In the pollen cell the plastids again revert to the 

 position which they had at early prophase of the pollen mother cell. 



