FERTILISATION 



29 



(Fig. 1 2, A). If prothalli be grswn in moist air, and only watered by 

 absorption from below, the archegonia will have no access to fluid water, 





FIG. 13. 



Fertilisation in Onoclca sensibilis : the arrows indicate direction of the growing point of 

 the prothallium. A. vertical section through an open archegonium probably within ten 

 minute? after the entrance of the first spermatpzoid. X 500. B. vertical section of the 

 venter of an archegonium containing spermatozoids, and the collapsed egg with a sperma- 

 tozoid within the nucleus. Thirty minutes. X 1200. (After Shaw.) 



and they will then remain closed, and fertilisation will be impossible ; but 

 if watered from above, as they would be in the ordinary course of Nature, 

 the external fluid water will bathe them, 

 and rupture will result. This may be 

 observed in living archegonia which 

 have been kept relatively dry, and then 

 mounted in water under the micro- 

 scope : the neck dehisces at the distal 

 end owing to internal mucilaginous 

 swelling, and its cells diverge widely: 

 the canal-cell and ventral- canal-cell are 

 extruded, and the ovum remains as a 

 deeply seated, spherical protoplast, while 

 access to it is gained through the open 

 channel of the neck (Fig. 12, B). Thus 

 the same conditions lead to the rupture 

 both of the male and female organs : 

 in Nature a shower of rain would supply 

 the necessary external fluid water, and 

 would at the same time supply the 



- 



FIG. 13 bis. 



Horizontal section of an egg, showing coiled 

 spiral male nucleus within the female. Twelve 

 hours. XI200. (After Shaw.) 



