M. W. Hofmeister on the Fertilization of Ferns. 273 



the latter has vanished by the time when the archegonium is 

 ready for impregnation. In the Ferns, as in the Equisetacese, 

 I never found more than one germinal vesicle in each arche- 

 gonium. In Salvinia, on the contrary, there are often two 

 present. 



During the formation of the canal traversing the neck of the 

 archegonium, the membrane at the apex of the central cell 

 becomes softened. The spermatozoids which enter this canal 

 make their way through the mucilage filling it, as far as the in- 

 terior of the central cell, where they move actively round about 

 the germinal vesicle, which is closely adherent to the vaulted 

 apex of the central cell near the internal end of the canal, with 

 its hemispherical free end hanging down in the cavity. In one 

 case, when these spermatozoids had arrived at the central cell 

 of an archegonium of Aspidium Fili^-mas, the movements lasted 

 for seven minutes from the commencement of the observation. 

 The cessation was accompanied (and probably caused) by the 

 coagulation of the albuminous substance of the fluid contents of 

 the central cell *. 



When spermatozoids occurred in the cavity of the central cell, 



- * This is the place to mention the mode in which I proceeded in my 

 investigations. When Fern spores are thickly sown, a number of the ger- 

 minating prothallia soon advance far beyond the rest. At the time when 

 the advanced ones have long ceased to produce antheridia, and bear 

 abundance of archegonia (which in closely-tufted erect prothallia are pro- 

 duced on both surfaces, and most abundantly on those having most roots), 

 those which have remained behind in their growth are beginning to be 

 covered with antheridia. If the crop is now kept with little moisture for 

 several weeks and then suddenly abundantly watered, a large number of 

 antheridia and archegonia simultaneously burst. Then, in a few hours 

 afterwards, the surface of the larger prothallia will be found almost covered 

 with moving spermatozoids. I now take such prothallia as exhibit freshly 

 opened archegonia, holding them by one wing between the linger and 

 thumb of the left hand, so that the upper face of the prothallium lies upon 

 the thumb, and with a thin, narrow knife make delicate longitudinal sec- 

 tions perpendicular to the surface of the parenchymatous part of the pro- 

 thallium. When the cushion-like thickening of the tissue is only ^th of 

 a line thick, after some practice it is not difficult to cut sections not more 

 than y^^th of a line broad. If such sections are quickly examined under a 

 power of 200 or 300 diameters, spermatozoids may sometimes be found in 

 the interior of the archegonia which are exposed in their whole length. I 

 once saw two, one close behind the other, in the canal of the archegonium 

 of Pteris aquilina, when their movements ceased during the observation ; 

 in the same Fern I saw one in motion in the central cell, at the side of the 

 germinal vesicle. In Asp. Filix-mas I have seen a spermatozoid moving 

 in the central cell, once more besides the case mentioned in the text ; and 

 in this, as well as in Asplenium septentrionale and Filiw-foemina, I have seen 

 motionless spermatozoids lying beside the partially-developed germinal 

 vesicle. Thus the unequivocal observations of moving spermatozoids in the 

 central cell amount only to three ; but these were so clear and distinct as 

 to exclude all possibility of deception. 



Ann. ^ Mac/. N. Hist. Ser. 2. Fr>/. xiv. 18 



