X FILICINE.-E LEPTOSPORANGIAT.E 315 



the venter of the ripe archegonium. The disintegration of the 

 division walls of the canal cells, and the partial deliquescence of 

 the inner walls of the neck cells, offer no peculiarities. 



When the archegonium opens, the terminal cells diverge 

 widely and the upper ones are often thrown off. 



The opening of the sexual organs and the entrance of the 

 spermatozoids may be easily seen by simply allowing the plants 

 to remain slightly dry for a few days until a number of sexual 

 organs are mature. If these are now placed upon the slide of 

 the microscope in a drop of water, in a few minutes the sexual 

 organs will open, and the spermatozoids will be seen to be 

 attracted to the archegonia in large numbers, and with care 

 some of them may be followed into the neck and down to the 

 central cell. The actual entrance of the spermatozoid into the 

 eesf has been observed, but is difficult to demonstrate in the 

 living condition. Pfeffer ^ has shown that the substance which 

 attracts the spermatozoids in the Polypodiaceae is malic acid, 

 and that an artificial solution of this, of the proper strength, 

 will act very promptly upon the free spermatozoids of these 

 Ferns. 



As soon as the egg is fertilised it develops a membrane, 

 and soon after undergoes its first segmentation. The inner 

 walls of the neck cells almost immediately turn dark brown, 

 and the cells of the ventral part begin to divide actively and 

 form the calyptra, which here, as in the Bryophytes, is formed 

 from the venter alone, and is tipped with the remains of the 

 neck cells. 



The position of the archegonium depends largely upon the 

 light. If both sides of the prothallium are about equally 

 illuminated, archegonia will develop from both sides. As soon 

 as an archegonium is fertilised, no new ones form, but it 

 frequently happens that a very large number prove abortive 

 before finally fertilisation is effected. 



The Embryo 



The first division wall in all Polypodiaceae yet investigated 

 is vertical and nearly coincident with the axis of the 

 archegonium. This basal wall (Fig. 160, I) at once divides 

 the embryo into the anterior epibasal half and the posterior 



1 Pfeffer (3). 



