CYCADALES 



21 



Cycas circinalis Treub J1 once or twice saw a transverse division 

 of one of the neck cells. 



The central cell is the only remnant of the " axial row " of 

 the lower Archegoniates, true neck canal cells having been 

 eliminated from, the history of the archegonium. The great 



FIG. 20. Cycas revoluta, development of archegonium : A, upper part of endosperm, 

 showing an archegonium initial (a) ; B, young archegonium, showing neck cell and 

 central cell; (7, a portion of the layer of jacket cells surrounding the central cell, 

 showing the cytoplasmic connections ; Z>, two cells of the jacket layer, showing the 

 passage of nuclear material into the central cell; E, F, G, successive stages in the 

 mitosis concerned in cutting off the ventral canal cell : A-C, x 200; D-G, x about 

 500. After IKENO. 



enlargement of the central cell and of its nucleus, during the 

 three months of organization, received special attention from 

 Ikeno, who explains the source of the large supply of nutritive 

 material needed. About the central cell the adjacent endo- 

 sperm cells are organized into a definite jacketlike layer (Fig. 



