120 



THE PLANT CELL. 



Fig. 91. — a, A portion of a longitudinal 

 section through a young anther of 

 Polygonatum, showing part of the 

 poUen-sao, filled with pollen mother- 

 cells in all stages of division, h, A 

 single mother-cell which has divided 

 into two, the cell-plate having just 

 been formed, c, The same after the 

 second division, walls being formed 

 at right angles to the first wall. 

 d, Four complete daughter - cells 

 (young microspores) still enclosed 

 by the wall of the original mother- 

 cell, e, A mature microspore. Three 

 cells are present, the uppermost one 

 being the prothallial cell, the middle 

 one the antheridial or generative 

 cell, and the lowest the vegetative 

 cell, from which ultimately the 

 pollen-tube is formed. 



