THE GAMETOPHYTE 



131 



States, however, that he has found them also upon the upper surface of the prothal- 

 Uum, but none of the specimens I have examined have shown this. The mother 

 cell of the young archegonium is scarcely distinguishable in form from the young 

 antheridium and like it is first divided by a periclinal wall into an outer cover cell 

 and an inner cell, the latter usually, but not always, divided subsequently into a 

 central and a basal cell (figs. 101-103), as in Ophioglossum and in the typical ferns. 

 Sometimes the mother cell of the archegonium is seen in transverse section to have 

 been cut out very much as the axial row of cells arises in the archegonium of the 

 Hepaticae. There seems no question that the so-called mother cell of the archego- 

 nium in all the ferns is really homologous only with the axial row of cells of the 

 bryophyte archegonium, the four rows of neck cells being a further development 

 of the terminal cap cell of the liverwort archegonium. 



The inner of the two primary cells, as we have already stated, may have a basal 

 cell cut off from it before the further divisions arise, by which the egg cell and the 

 canal cells are divided. The neck canal cell is very broad and may become divided 

 into two cells, but usually the division is confined to the nucleus, which probably 

 divides in all cases. The ventral canal cell cut off in the usual fashion from the egg 

 is, with the exception of Dancea, very large and conspicuous, thus differing from 



Fig. ioi. 

 Archegonia of ^ng<'o^<eri5. X275. i, basal cell; u, egg; i;, ventral canal cell. 



Ophioglossum, where the ventral canal cell is so difficult to demonstrate; but in 

 Dancea there is the same imperfect development of the ventral canal cell that is 

 found in Ophioglossum. 



As the archegonium approaches maturity a layer of mantle cells, much like 

 those which surround the antheridium, is cut off from the tissue surrounding the 

 venter of the archegonium. The archegonia of Mar atti a douglasii are confined to 

 the lower side of the midrib and begin to form at some distance back of the grow- 

 ing point; so far as can be determined, any superficial cell of the apical meristem 

 can develop into an archegonium. The mother cell divides, as we have seen, 

 into three superimposed cells, of which the lowest, h, usually divides later by 

 vertical walls, and forms the base of the archegonium. From the central one, by 

 transverse divisions, are formed the canal cells and egg, and from the uppermost 

 the neck. Compared with the typical ferns, the most striking differences are the 

 short neck and the very broad canal cells. The cover cell undergoes division into 

 four, by two intersecting vertical walls, as in Ophioglossum, and each of these four 

 cells then undergoes division by nearly horizontal walls, but the cells remain short, 

 so that the neck projects very little and there are only three or four cells in each row; 

 occasionally there may be only two. Jonkmann states that, as a rule, two of the 

 rows of the neck contain three cells and two contain four, but that there may occa- 

 sionally be as many as five. The neck canal cell often shows a trace of a division and 

 there may be an actual division wall formed (fig. loi, D), but in Marattia douglasii 



