448 THE FERTILIZATION AND DEVELOPMENT OP FLORIDE^E. 



The sporogenous nucleus, after remaining for a while in the 

 centre of the fused cell, moves outwards towards the sporogenous 

 half of the cell, which at the same time begins to grow out into a 

 slight protuberance. Here the protoplasm then congregates, leaving 

 the auxiliary nucleus almost bare at the far end of the cell. This 

 protuberance grows out into the new sporogenous-filament, which 

 then works its way between the vegetative branches of the thallus. 

 This is the order of growth for the two outer sporogenous-filaments, 

 arising from the fertilized carpogonium ; the middle filament, when 

 present, fuses with cells which lie in the middle of the carpogonial 

 branch and also with cells which arise as off-shoots from the pinn^ 

 described above. This shows, as Prof. Oltmanns points out, that 

 though the terminal cells of the pinnas are more especially adapted 

 to form auxiliary-cells, almost all the cells of the carpogonial branch 

 are capable of taking on this character, although the terminal cells 

 appear to possess a special quantity of food material. 



Now to follow the farther development of the sporogenous- 

 filaments. They grow out, as is well known, towards the terminal 

 cells of side-branches which arise at the base of the ordinary 

 vegetative branches. The terminal cells of these side-branches 

 are slightly different in appearance from the other cells of the same 

 branch and the sporogenous-filament works its way towards this 

 terminal cell and fuses with it. Division of the sporogenous nucleus 

 has previously taken place, and while one sister-nucleus is carried 

 on by further growth of the sporogenous-filament to other auxiliary- 

 cells, the other remains in the fused cell which is now cut off from 

 the sporogenous-filament by a cell-wall. The behaviour of the 

 two nuclei, that from the sporogenous-filament and that of the 

 original auxiliary-cell, now together in the fused cell, is exactly the 

 same as that described above in the fusion of the sporogenous- 

 filament and the auxiliary-cell of the carpogonial branch. The 

 sporogenous nucleus remains where it was left after subdivision, 

 that is, at the junction of the sporogenous-filament and the auxiliary- 

 cell, while the auxiliary nucleus gives the idea of being driven back 

 against the further wall of the auxiliary-cell. As the fused cell 

 increases in size, so the auxiliary nucleus decreases. Again, as 

 before, the protoplasm of the fused cell gathers round the sporo- 

 genous nucleus, which then divides into two. Immediately cell- 

 division takes place across the fused cell, between the two sporo- 

 genous sister-nuclei ; and while one nucleus wanders to any part of 

 the fused cell, the other departs to the furthest end of the cell 

 which is cut off from the main mass of the fused cell. This newly 

 formed cell, of purely sporogenous origin, except for any protoplasm 

 which may possibly have entered from the auxiliary-cell, divides 

 up and forms the spores. The development of these is of course 

 well-known. 



It is seen therefore that though there is absolutely no fusion of 

 nuclei after the first act of fertilization, yet no further development 

 takes place from the junction of the sporogenous-filament and the 

 auxiliary-cell, unless a sporogenous nucleus is left behind in the 

 auxiliary-cell. Prof. Oltmanns points out that according to Prof. 



