312 MOSSES AND FERNS chap. 



the top. The young antheridium at this stage consists of 

 four cells — a central dome-shaped one surrounded by three 

 others, the two lower ring-shaped, and the terminal one discoid. 

 These outer cells are nearly colourless, and contain very little 

 granular contents, except the small chloroplasts, which are 

 mainly confined to the surface of the inner walls. 



The divisions in the central cell are at first very regular. 

 The first one is always exactly vertical, and is followed by a 

 transverse wall in either cell which strikes it at right angles, 

 and next a third set of walls at right angles to both of these, 

 so that whether seen in cross-section or longitudinal section, 

 the central cells are arranged quadrant -wise. Successive bi- 

 partitions follow in all the cells until the number may be a 

 hundred or more, but the number is usually much less, about 

 thirty-two being the commonest. The regular arrangement of 

 the sperm cells soon becomes lost, and they form a mass of 

 polyhedral cells with dense granular cytoplasm, and large 

 nuclei. A nucleolus is visible until the last division, after 

 which it can no longer be distinguished ; otherwise the nuclei 

 show no peculiarities. The transformation of the nucleus into 

 the body of the spermatozoid proceeds here as in other Ferns 

 that have been examined, but I was unable to satisfy myself 

 that so large a part of the forward end of the spermatozoid is 

 of cytoplasmic origin, as Strasburger ^ asserts. The fully- 

 developed spermatozoid describes about three complete coils 

 within the globular sperm cell, and does not lie coiled in a 

 single plane, as in the Hepaticae, but in a tapering spiral (Fig. 

 157, D). The very numerous long cilia are attached at a 

 point a short distance back from the apex, and as Buchtien - 

 showed, cover a limited zone, although hardly so restricted as 

 he figures. 



The separation of the sperm cells begins at about the time 

 the development of the spermatozoids commences. The 

 mucilaginous walls stain now very strongly, and in a living 

 state appear thick and silvery-looking. The central lamella 

 of the cell wall, however, remains intact, so that vrhen the 

 spermatozoids are ejected, they are still enclosed in a delicate 

 cell membrane, which swells up as the water is absorbed and 

 finally dissolves completely. - The vesicle derived from the 

 remains of the cytoplasm is very conspicuous here, and the 

 1 Strasburger (11), vol. iv. p. 115. . ^ Buchtien (i),.p. 38. 



