BRYOI'HYTES 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 v „ a ' \ ,, . 



J Fig. 238. — 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 the c Sg- ventral canal cell, and 



the outer cell divides transversely, giving rise to four ncck canal cells) ca PP ed b ? 



the cap cell and the primary ncck canal cell; the thc L nt ' ck . cclls < two ^^i in th , c 



„ . ., t . , , ,, . . archegonium to the left, the neck 



inner cell is the primary ventral cell; thc primary „ , > .. « .. 



r y * J cells have been thrown off, thc 



neck canal cell, by two successive divisions, cana , t ,. ]ls h;m , disorganizcd> and 



develops a row of four neck canal cells ; the tnc 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). 



