THE GAMETOPHYTE 



29 



In Ophioglossum the young archegonia may be found near the apex of the 

 prothallial branch, but they may also arise at a considerable distance back of it. 

 In general, Hke the antheridia, they arise in acropetal succession. 



The mother cell, like that of the antheridium, is sometimes broad, sometimes 

 narrow and deep, and the cover cell is correspondingly shallow, or deep. The first 

 division of the inner cell takes place shortly after the cover cell is cut off. The next 

 division is in the cover cell, which first divides by a vertical wall, a second vertical 

 wall being formed almost immediately, intersecting the first and dividing the cover 

 cell into four practically equal cells, arranged quadrant-wise (fig. i6. A). The 

 middle cell next divides by a transverse wall into the primary neck canal cell and 

 the central cell (fig. i6, F). The canal cell pushes up between the four primary 

 neck cells, which presently divide by nearly horizontal walls, so that there are two 

 tiers of neck cells. One or both of these divide again later, so that each row of neck 

 cells consists of three or four. Rarely there may be five cells in one or more of the 



rows. 



Fig. i6. — Development of the archegonium in Ophioglossum pendulum. Xi8o. 



A. Transverse section of gamctophyte apex, showing two young archegonia, 9 , and apical cell, x. 



B-G. Successive stages in the development of the archegonium; seen in longitudinal section; «, neck canal cell; 6, basal cell. 



H. Recently fertilized archegonium; sp, a spermatozoid within the egg nucleus. 



The neck canal cell is very conspicuous, its base being broad, and the upper 

 part narrower and extending to the uppermost neck cells. The large and conspicu- 

 ous nucleus soon divides into two, but as a rule there is no division wall, although 

 occasionally two distinct neck canal cells may be present. Sometimes both of the 

 nuclei remain in the broad basal part of the cell, and sometimes one is at the base 

 and one nearer the apex. This arrangement seems to depend upon the direction 

 in which the nuclear division takes place. 



The basal cell divides by a vertical wall at about the same time that the primary 

 canal cell is cut off from the central cell. The basal cell subsequently undergoes 

 further divisions, but its limits are readily distinguishable up to the time that the 

 archegonium is mature (fig. i6, G). 



In its earlier stages, the archegonium of Ophioglossum pendulum bears a 

 striking resemblance to that of the Marattiaceae, which the mature archegonium 

 more nearly resembles than it does that of Botrychium. According to Bruchmann's 

 account, O. vulgatum has a neck somewhat longer, and this is also true of 0. moluc- 

 canum. Even when mature, the neck projects but little above the surface of the 

 prothallium, although there is some elongation of the cells at the time of dehiscence 

 (fig. i6, G). 



The ventral canal cell is very difficult to demonstrate, and one is sometimes 

 inclined to doubt whether it is formed at all in some cases; neither Lang nor Bruch- 



