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 Hepaticae, and the further development 

 corresponds with these, except that the base of the archegonium 



FlG. 44. Fossombronia longiseta. Development of the archegonium, longitudinal sec- 

 tion, XS2s; 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 well 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 number is con- 

 stant cannot be stated positively. The female branch remains 



