io8 



MOSSES AND FERNS 



CHAP. 



the short but evident pedicel of the archegonium. The latter 

 is very like that of the anacrogynous Liverworts. Of the three 

 first walls (Fig. 54, C), the last formed one is much shorter, 

 so that one of the three peripheral cells is much smaller, and 

 does not divide by a vertical wall, and the neck has but five 

 rows of cells, as in Pellia. This appears to be universal 

 among the acrogynous Jungermanniales examined. Often in 

 Porella the three primary w^alls converge at the bottom so as 

 to almost meet, in which case the central row of cells is nar- 

 rower at the base (Fig. 54, D). The rest of the development 



Fig. 54. — Porella Bolanderi. Development of the archegonium, X6oo; C, cross-section 

 of young archegonium; G, cross-section of the neck of an older one. The others 

 are longitudinal sections; b, ventral canal cell; o, the egg. 



is exactly as in the other Hepaticse. The number of neck 

 canal cells in the full-grown archegonium is normally eight. 

 The archegonium (Fig. 54, F), at maturity is nearly cylin- 

 drical, with the venter but little enlarged. The canal cells are 

 broad, but the ^gg small. The venter has a two-layered wall. 

 The first-formed archegonia arise in strictly acropetal sue- 



