FERNS. 



343 



and outer one produces by further divisions the neck, which, when mature, consists 

 of four rows of cells meeting in its axis. A layer of cells is formed by division of the 

 cells surrounding the central cell, corresponding to that of the wall of the ventral 

 part of the archegonium of Muscineoe. The further changes which take place 

 within the central cell, and the formation of the canal of the neck, are described by 



FiC. 253 — Amlicridia >.>( Adiaiiluin Cnpillits-l'eneris (X 550), in loiijjitiKlinal optical section ; / not yet ripe ; 

 // the antherozoids already mature ; /// the antheridiuni burst, the parietal cells greatly swollen radially, the 

 antherozoids mostly escaped ; / prothallium, a antheridiuni. s antherozoid, b the vesicle containing starch- 

 grains. 



Strasburgcr and Kny in the works already mentioned, in accordance with my earlier 

 observations; so that the drawing, Fig. 255, given in my first edition, can be re- 

 tained ; it is completed by Fig. 254, borrowed from Strasburger, which represents 

 a younger condition of development. The contents of the central cell are divided 



^ A 



Fig. 254.— Young archegonia oi Pteris serriilata (after Strasburger) ; 



the oosphere, h h the neck, k the canal-cell. 



into two unequal portions; the larger and lower one (Fig. 254, A, e) is at first 

 broad, almost discoid, and afterwards becomes round ; it is the oosphere. The 

 other portion {k), which is at first smaller, grows in between the four rows of cells 

 of the neck, forcing them apart ; it thus forms a canal filled with mucilaginous 

 protoplasm, in which a row of nuclei arises, but without the corresponding cell- 



