274 



STRUCTURAL BOTANY 



the pointed nucellus, nc. Most of its lower part is 

 occupied by the large oval embryo-sac, which is shaded 

 to indicate that it is filled with prothallus, e. Two of 

 the archegonia are shown in section. 



FIG. 113. A, Upper part of embryo-sac in longitudinal 

 section, showing two archegonia : o, ovum of an arche- 

 gonium ; c, neck ; cl, ventral canal cell ; n, n, nuclei of the 

 two ova. B t Portion of upper surface of prothalltis, 

 showing the neck of an archegonium, c. C, Enlarged 

 longitudinal section passing through the neck of an 

 archegonium at the time of fertilisation. The pollen- 

 tube, p.t, has penetrated the neck. Near the lower end of 

 the tube its two generative nuclei are seen. Magnified 

 A, about 50 diameters ; , about 125 diameters ; C, about 

 125 diameters. (After Strasburger. ) 



The archegonia are the true female organs, in which 

 fertilisation takes place. Just before the archegonium 



