BRYOPHYTES 



107 



Antheridium. The antheridia are embedded in the thallus and are 

 therefore hard to detect (fig. 237). The antheridial initial is a superficial 

 cell, but it does not develop a papillate protrusion as in the other liver- 

 worts. A transverse (periclinal) wall divides it into an outer and an 

 inner cell. In the other groups the outer cell develops the antheridium, 

 but in Anthocerotales the antheridium is developed from the inner cell. 

 By a succession of anticlinal and periclinal divisions, the outer cell 

 produces two layers of cells, which form an outer wall or roof to the 

 antheridial chamber. 



The inner cell develops one to several antheridia. The method of development 

 of an antheridium, whether directly from the inner cell or from one of its daughter 

 cells, is as follows : two vertical walls at right angles to each other result in four 

 cells ; transverse walls result in several tiers of four cells each ; periclinal walls in 

 the upper tiers cut off an outer wall layer and an inner group of spermatogenous 

 cells and the lower tiers (sometimes only the lowest) develop a more or less elon- 

 gated stalk. The antheridium or group of antheridia thus produced lie in what 

 may be called an antheridial chamber (fig. 237). 



Archegonium. The archegonia also are in the tissue of the thallus. 

 in this respect resembling the archegonia of pteridophytes (fig. 238). 

 In all other bryophytes they are entirely 

 superficial structures. As a result of this 

 relation to the thallus, there are no sterile 

 jacket cells (neck and venter) very dis- 

 tinct from the adjacent cells of the thallus. 

 The essential part of an archegonium, 

 however, is the axial row, and in the 

 Anthocerotales this is the only distinct FlG 2 ^ __ Anthoceros : arche . 



Structure. gonia, showing " embedded " char- 



acter; in the archegonium to the 



The general outline of development of this right the complete axial row is 

 axial row is as follows: a superficial cell divides shown (beginning below, the cells 

 transversely, giving rise to outer and inner cells ; are tne e 8g ventral canal cell, and 

 the outer cell divides transversely, giving rise to four neck canal celk ) ca PP ed b ^ 



the cap cell and the primary neck canal cell; the the neck . cells ( tw v ' sible )> in the 



.... . ,,,. archegonium to the left, the neck 



inner cell is the pnmary -ventral cell ; the primary ^ haye been thrown ^ ^ 



neck canal cell, by two successive divisions, canal cells haye disorganized , and 

 develops a row of four neck canal cells ; the the re is a passageway open to the 

 primary ventral cell, by a single transverse egg, which is ready for fertilization, 

 division, forms the ventral canal cell and the 



egg. At maturity the cap cells are thrown off, the neck and ventral canal cells 

 break down, and a broad canal is open to the egg (fig. 238). 



