124 GYMNOSPERMS 



to another; but, as the central cell becomes large, a definite layer of 

 cells, called the "archegonial jacket," appears. As the jacket be- 

 comes more and more differentiated, the egg membrane thickens and 

 finally becomes so tough that it retains its form and connection with 

 the suspensor, even when embryos half the length of the seed are dis- 

 sected out. In the ripe seed this resistent egg membrane can still be 

 recognized. In an early stage it is easy to see that it has numerous 

 large pits into which the turgid protoplasm of the egg presses. For 

 some time the pits are covered by a thin membrane, the middle 

 lamella between the wall of the jacket cell and that of the egg. The 

 cells of the female gametophyte are full of starch, proteid, and prob- 

 ably other materials which find their way through the archegonium 

 jacket and into the egg in the usual manner. 



But the growing egg becomes so turgid that the papillae, or haus- 

 toria, as they may be called, break the thin membrane, which closes 

 the pit, thus leaving the haustoria of the egg in direct contact with 

 the protoplasm of the jacket cell, so that materials can pass from the 

 jacket cell into the egg as readily as from one part of a cell to another 

 (figs. 124-29). 



The turgidity of the female gametophyte, and, later, the turgidity 

 of the central cell, and, still later, the egg cell, is extreme. In trim- 

 ming material for fixing, if one cuts too near the jacket, the young 

 gametophyte breaks through. At the fertilization period, and for a 

 month before that time, if one cuts too near the jacket, there may be 

 a rupture several millimeters in length. If one cuts into the endo- 

 sperm too near the archegonial jacket, there will be a small rupture 

 of the egg membrane and cells nearest to it, and the liquid contents 

 of the egg will spurt out, sometimes to a distance of 20 cm. 



Shortly before the nucleus of the central cell divides, the tissues 

 around the archegonial region grow rapidly, leaving the archegonia 

 in a depression called the "archegonial chamber." 



Immediately after the mitosis which gives rise to the ventral canal 

 nucleus and the egg nucleus, the ventral canal nucleus begins to dis- 

 organize and soon disappears, while the egg nucleus moves toward 

 the center of the egg, increasing immensely in size, until it sometimes 

 reaches a diameter of 500 microns, easily visible to the naked eye. 

 During this time the chromatin, easily distinguishable in the late 



