STRASnURGER ON THE FERTILISATION OF FERNS. 773 



into the mouth of the current. A diffusion current cannot here be assumed, and 

 just as little a vortex suddenly seizing the antherozoids and hurling them 

 towards the opening, since even very minute granules remain completely at rest 

 in front of the opening of the canal. The motion of the antherozoid in the slime 

 is decidedly slower, but it does not cease to revolve about its axis. The slime, 

 however, leads it into the canal, so that its action here may be compared with 

 the activity of the stigmatic fluid and the conducting tissue, which conduct the 

 pollen-tube of the phanerogams to the ovule. At the same time we can here 

 convince ourselves most decidedly how little warranted is E. Roye's assumption that 

 it is the vesicle at the hinder part of the antherozoid which contains the ferti- 

 lising substance. Most of the antherozoids have already lost this vesicle before 

 they even come at the archegonium ; others which still possess it now lose it in 

 the slime, and none take it with them into the interior of the archegonium. I 

 have, among others, exactly recorded a case in Cera/op/ens, where five anthero- 

 zoids just escaped from their antheridium, penetrated into the central-cell, and 

 six such vesicles were to be noticed in the slime before the opening of 

 the neck.' 



' Arrived at the interior of the canal, the coils of the antherozoid become 

 drawn widely apart and, if no other disturbing influences affect it on the way, it soon 

 reaches the interior of the central cell, where the emptied canal-cells have left a suffi- 

 ciently large cavity. Here the coils again contract, and the movements again become 

 freer. The first antherozoid that penetrates usually does not remain the only 

 one, but others soon follow it : their number inside the central cell may amount to 

 four or even five, so large is the space here afforded by the canal-cells. They then 

 move actively in and out and between one another, somewhat like the antherozoids 

 which remain behind in an antheridium, Antherozoids coming later remain stuck 

 in the canal of the neck : in Pteris serrtdata their number may increase enormously, 

 each new arrival screwing itself in between those already present so long as its 

 movements are still possible, and at last becoming extended quite straight. It thus 

 happens that in some cases the canal of the archegonium appears as if filled 

 with long threads. New antherozoids now arriving can no longer be taken in; 

 I have however observed a few cases in Pteris where they nevertheless screw 

 themselves with their anterior ends between the previous arrivals, and there is 

 thus formed a great struggling crowd of antherozoids, extending radially from 

 the canal. 



' In this crowd some of them are seen to revolve about their axes for 

 some time longer, and sometimes even to get loose again and hurry away. In 

 Pteris serrulata I have repeatedly counted over a hundred antherozoids in 

 such a crowd, and even half an hour after the entrance of the first antherozoid 

 a few still remain fixed in the slime. Such aggregations, it is true, are 

 exceptional, and the number of the antherozoids which enter into an archegonium 

 is usually limited to a few only ; these aggregations moreover only occur in the 

 case of Pteris, they are not possible in the case of Ceratopteris ; not only because the 

 prothallium here developes relatively few antherozoids, but also because the slime 

 expelled from the neck of the archegonium diffuses far more quickly in the surround- 

 ing water, and only holds for a short time the antherozoids which are hurrying by. 



