348 



MOSSES AND FERNS 



CHAP. 



fertilisation, where the spermatozoid may be seen but little 

 altered in form. It almost at once comes into contact with 

 the female nucleus, and the two then move toward the centre 

 of the ovum. Here the spermatozoid gradually loses its coiled 

 form and contracts until it becomes oblong, and in close 

 contact with the egg nucleus, in some cases looking as if it 

 were actually within it. The process is a slow one, and in one 

 case twenty-four hours after the entrance of the spermatozoid 

 the two nuclei were still recognisable. Finally they are 

 completely fused, and a single nucleus, with usually, perhaps 

 always, two nucleoli is seen. No sign of a separation of the 

 chromosomes of the copulating nuclei was observed. 



The Embryo 



The first division of the ovum is the same with respect to 

 the archegonium as in Onoclea, i.e. the basal wall is parallel 



c. 



Fig. 176. — A, Vertical section of an eight-celled embryo of O. Claytotiiana, X260. Median 

 longitudinal section of an older embrj-o of the same species, X260 ; C, two transverse sections of 

 a somewhat younger embryo of O. cinnamoiiiea, X 260 ; si, stem apex ; L, cotyledon ; r, primary 

 root ; F, foot. 



with its axis ; but the quadrant wall is also parallel with this 

 instead of transverse, although its position with reference to the 

 axis of the prothallium is the same ; so that the embryo- 



