THE ANCIENT FERNS 



1904. The sunken sex organs are well seen in Fig. 266, with some additional details of the 

 opening of archegonia, etc., depicted in Fig. 265. As was observed by Bruchmann, June 

 is the first month in which mature sex organs can be found, but from June till September 

 it is easy to observe both the liberation of spermatozoids and the opening and impregna- 



V 



c 



< 



K 



Fig. 264. Prothalli of Ophioglossum vulgatum L. found in Cheshire 

 and preserved in alcohol. Natural size. 



Fig. 265. Sexual reproduction in living prothalli of Ophioglossum vulgatum L. in the month of July. 

 c. Part of a prothallus in water showing two of the neck cells of a freshly opened archegonium 

 opposite the arrow, x about 100. b. A spermatozoid recently emerged and killed in iodine to 

 show the cilia, x about 200. 



tion of archegonia. Some observations to illustrate this are contained in Fig. 265, in 

 which Fig. 265/) shows a newly emerged male gamete killed with a drop of iodine 

 and photographed at once, and Fig. 265 a a living prothallus with the neck of a newly 

 opened archegonium projecting beyond the solid tissue. The size of the neck cells in 

 relation to the whole prothallus can be judged by noticing the white patch on the lower 

 side of the picture which marks the other side of the prothallus. A short time after 



266 



