92 



MOSSES AND FERNS 



CHAP. 



later showing a division into ventral and dorsal cells. Prob- 

 ably this type has been derived from the former by a gradual 

 increase in the size of the angle formed by the dorsal and ven- 

 tral walls of the apical cell, which finally became so great as 

 to practically form one plane. 



. The antheridium of PcUia is larger than that of Aneura, 

 but its development is very similar except that the stalk is 

 multicellular, as it is in the other Anacrogynae. The sperma- 

 tozoids of Pellia (Fig. 40, D, E), are much larger than those 

 of Aneura, but are exceeded in size by those of the allied genus 

 Makinoa (Miyake (2)). 



Fig. 43. — Fossombronia longiseta; early stages in the development of the antheridium, 

 X525; drawings made by Mr. H. B. Humphrey. D, cross-section. 



In Fossombronia (Fig. 43), which in several respects re- 

 calls Sphccrocarpns or Geothalliis, the first divisions in the an- 

 theridium are median ones, so that in both longitudinal and 

 transverse sections the antheridium appears to be divided into 

 equal quadrants. The first division, however, is vertical, as it 

 is in Aneura. 



The archegonia are borne upon similar but shorter 

 branches and tlieir development also is very regular. In Fig. 40, 

 B, a vertical section through the end of a young female branch 

 is shown with the apical cell {x). Segments are here, too, cut 



