344 



MOSSES AND FERNS 



CHAP. 



lower surface of the wings. The development corresponds 

 closely in all forms that have been examined, and differs 

 considerably from that of the Polypodiaceae. 



The mother cell is cut off as usual, but the second wall is 

 not funnel-shaped, but plane and inclined, so that it strikes the 

 basal cell. In the larger of the two cells thus formed a vary- 

 ing number of divisions occur, cutting off a series of lateral 

 segments, much after the fashion of a three-sided apical cell. 

 The segments thus cut off form the basal part of the antheridium, 

 and when the number is large a pedicel may be formed. When 

 the full number of basal segments is complete, a dome-shaped 



B 



Fig. 173. — A-D, Development of the antheridium of O. ciniiainoniea, in longitudinal section, 

 X425 ; E, F, G, three surface views of a ripe antheridium of O. Claytoniana; E, from above, 

 Ihe .others from the side ; o, opercular cell, X425. 



wall arises in the apical cell, as in the Polypodiaceae, and the 

 central cell has much the same form (Fig. 173, A). This has 

 no chlorophyll, and as usual the large distinct nucleus is 

 embedded in dense highly refractive cytoplasm. There are 

 next formed in the outer dome-shaped cell two or three walls, 

 running more or less obliquely over the apex ; either at the top 

 or at one side the last-formed wall encloses a small cell, which 

 is thrown off when the antheridium opens (Fig. 173, 0). This 

 opercular cell, both in form and position, recalls strongly that 

 found in the Marattiaceae. 



The divisions in the central cell correspond closely to those 



