IX 



MARA TTIA CE^E—ISOE TA CE/E 



261 



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

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

 very broad and the &^'g 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. 134, D). The 

 neck of the ripe archegonium projects but little above the 

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



Fig. 134. — Marattia Dou^iasii (Baker). A-D, Development of the archegonium, x 450 ; E, section of 

 the fertilised egg, showing the spermatozoid (s/) in contact with its nucleus, X485 ; F, successive 

 longitudinal sections of a young embryo, X225 ; 6, b, the basal wall, the arrow points towards the 

 archegonium. 



lower Ophioglossaceae and the Anthocerotese. The ripe ovum 

 is somewhat elliptical, and slightly flattened vertically. Its 

 upper third is colourless and nearly hyaline. This is the 

 " receptive spot," and it is here that the spermatozoid enters. 

 The nucleus is of moderate size, and not rich in chromatin ; a 

 small but distinct nucleolus is present. The spermatozoid 



retains its original form after it first enters the egg, and until it 

 comes in contact with the membrane of the egg nucleus. It 

 afterwards contracts and assumes much the appearance of the 



