142 BOTANICAL GAZETTE [august 



has been reached by several lines of development; hence close rela- 

 tionship with "Acrogynae" is not necessarily implied. If the 

 development of the antheridium may be taken as a basis of classi- 

 fication, it would seem that Pellia arose from the main line of 

 advance before the two branches, Jungermanniales and Mar- 

 chantiales, became separate, even before the archegonium and 

 antheridium became definitely differentiated in their methods of 

 development. 



From Pellia we have evidence regarding the relation of Jun- 

 germanniales and Marchantiales. There is in the life history a 

 transition from the cuneate apical cell of Marchantiales form to the 

 lenticular cylindrical apical cell found in certain Jungermanniales; 

 similarly, the antheridium, already discussed, affords strong evi- 

 dence for the existence of such a relation. The evidence tends to 

 indicate that Marchantiales are primitive and that Jungermanniales 

 are derived. 



Summary 



The antheridium. — The development varies. The dominant 

 method is that characteristic of Jungermanniales; forms occur, not 

 infrequently, which are like the antheridium of Marchantiales, while 

 others are like the archegonium in their early development. 



The archegonium. — The archegonia are produced from cells of 

 the apical group and occur in an archegonial pocket. The diver- 

 sities from the regular form are few; the large number of neck 

 canal cells, the extreme development of the cap, the frequent 

 reduction of the number of tiers of neck wall cells to five, and 

 the somewhat massive venter may be noted. The outer cell of the 

 two resulting from the division of the archegonial initial divides 

 horizontally before the vertical wall is formed. 



Methods of growth. — Several periods of growth may be recog- 

 nized, each having a specific method of growth: the massive; the 

 period of the cuneate apical cell extending until antheridium 

 formation; the period of the lenticular cylindric apical cell, or the 

 antheridial period; the period of regional apical growth, or the 

 period of archegonium production; and the second period of mas- 

 sive growth, or the period of sporophyte dependence. 



