280 



MOSSES AND FERNS 



CHAP. 



the central cell. Each of these divides again transversely. In 

 the upper one this division is -often incomplete and confined to 

 the nucleus; but in the central cell the division results in the 

 separation of the ventral canal cell from the ovum. Before the 

 separation of the primary neck canal cell from the central cell, 

 the cover cell divides as in the Liverworts into four cells by 

 intersecting vertical walls, and each of these cells by further 

 obliquely transverse walls forms a row of about three cells, and 

 these four rows compose the short neck. The canal cells are 



FIG. 153. Marattia Douglasii. A-D, Development of the archegonium, X4So; E, sec- 

 tion of the fertilised egg, showing the spermatozoid (sp) in contact with its nu- 

 cleus, X48s; F, successive longitudinal sections of a young embryo, X22$; b, b, 

 the basal wall; the arrow points towards the archegonium. 



very broad and the egg cell small, so that after the archegonium 

 opens it occupies but a small part of the cavity left by the 

 disintegration and expulsion of the canal cells. Before the 

 archegonium is mature, flat cells are cut off from the adjacent 

 prothallial tissue as in the antheridium (Fig. 153, D). The 

 neck of the ripe archegonium projects but little above the 

 surface of the prothallium, and in this respect recalls both the 

 lower Ophioglossacese and the Anthocerotes. The ripe ovum 

 is somewhat elliptical, and slightly flattened vertically. Its 



