Ill 



THE JUNGERMANNIALES 



93 



off alternately right and left, and from each segment an arche- 

 gonium develops. The segment is first divided, probably, as 

 in the male branch and the vegetative ones, into an inner and 

 an outer cell, but I did not succeed in getting satisfactory longi- 

 tudinal sections parallel to the surface, so cannot speak posi- 

 tively on this point. The youngest segment, in which the 

 archegonium mother cell is recognisable, shows in vertical sec- 

 tion three cells, a small ventral one, a middle larger one, and 

 a dorsal one — the archegonium mother cell. The latter does 

 not form any stalk, but divides at once by the three intersect- 

 ing walls, as in other Hepaticse, and the further development 

 corresponds wdth these, except that the base of the archegonium 



B. 



Fig. 44. — Fossomhronia longiscta. Development of the archegonium, longitudinal sec- 

 tion, X52S; drawings made by Mr. H. B. Humphrey. 



is not free, and the central cell is below the level of the super- 

 ficial cells of the thallus. The archegonium neck is short, and 

 the basal part as w^ell as that part of the venter which is free, 

 two cells thick (Fig. 40, C). The number of neck cells is 

 small (apparently about four), but whether the numl^er is con- 

 stant cannot be stated positively. The female branch remains 



