Ill 



THE JUNGERMANNIALES 



109 



cession, and finally the apical cell divides by a transverse wall, 

 and the outer cell so formed becomes transformed into an 

 archegonium. In a numljer of cases observed, young arche- 

 gonia were noticed among the older ones, apparently formed 

 secondarily from superficial cells between them, and not from 

 the younger segments of the apical cells. 



A perianth is formed about the group of archegonia, much 

 as in the anacrogynous forms. 



Gayet ( i ) has asserted that in the Liverworts, as well as 

 in the true Mosses, the growth of the archegonium is largely 

 apical. This point has been examined again by the writer 

 (Campbell (21)), but Gayet's conclusions were not verified. 



c. 



Fig. 55. — Porella Bolanderi. Development of the embryo. A-D, in longitudinal sec- 

 tion; E-G, transverse sections. B and C are sections of the same embryo, and 

 E, F, G are successive sections of a single embryo, X525. 



The Sporophyte 



The early divisions in the embryo of Porella are less regu- 

 lar than those in some others of ^the foliose Liverworts. The 

 embryo at first is composed of a row of cells, of which the 

 lowest, cut off by the first transverse wall, undergoes here no 

 further development. Li Jungennannia bienspidata (Hof- 

 meister, Kienitz-Gerloff, Leitgeb) this lower cell undergoes 

 further divisions to form the filamentous appendage at the base 

 of the sporogonium. The next divisions in the upper part of 

 the embryo correspond closely to those described in Pellia and 

 Anenra, but the succession of the walls is more variable and 



