352 



MOSSES AND FERNS 



CHAP. 



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 anther- 

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

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

 shaped wall arises in the apical cell, as in the Polypodiacese, and 

 the central cell has much the same form (Fig. 195, A). This 

 has no chlorophyll, and as usual the large distinct nucleus is 

 embedded in dense highly refractive cytoplasm. There are 



Fig. 195. — A-D, Development of the antheridium of O. cinnamomea, in longitudinal 

 section, X42S; E, F, G, three surface views of ripe antheridia of O. Clay- 

 toniana; E, from above, the others from the siOe; 0, opercular cell, X425. 



next developed 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. 195, o). This 

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

 found in the Marattiaceas. 



The divisions in the central cell -correspond closely to those 

 in Onoclea, but the number of sperm cells is larger, being usu- 

 ally 100 or more. The development is also the same, and will 

 not be entered into here.^ After the final division of the sperm 

 cells the nuclei remain slightly flattened in the plane of division, 



^ For details see Campbell (12), p. 61, 



