318 



MICROSCOPIC FORMS OF VEGETABLE LIFE. 



Fio. 107. 



increased nutrition, for it is seen to project, carrying the cellulose 

 envelope before it, so as to form a little protuberance ; and this 

 sometimes attains a considerable length, before any separation of 

 its cavity from that of the cell which gave origin to it, begins 



to take place. This separation is gradu- 

 ally effected, however, by the infolding 

 of the primordial utricle, just as in the 

 preceding case ; and thus the endo- 

 chrome of the branch cell is com- 

 pletely severed from that of the stock. 

 The branch then begins to elongate 

 itself by the subdivision of its first- 

 formed cell ; and this process may be 

 repeated for a time in all the cells of the 

 filament, though it usually comes to be 

 restricted at last to the terminal cell. 

 The Confervacece multiply themselves 

 by " zoospores," which are produced 

 within their cells, and are then set 

 free, just as in the Ulvacefe (§ 195) ; in 

 most of the genera, the endoehrome 

 of each cell divides into numerous 

 zoospores, which are of course very mi- 

 nute ; but in (Edogonium, — afresh-water 

 genus distinguished by the circular 

 markings which form rings round the 

 extremities of many of the cells, and 

 by many interesting peculiarities of 

 growth and reproduction,' — only a 

 single large zoospore is set free from 

 each cell ; and its liberation is accom- 

 plished by the almost complete fis- 

 sion of the wall of the cell through 

 one of these rings, a small part only remaining uncleft, which 

 serves as a kind of hinge, whereby the two parts of the fila- 

 ment are prevented from being altogether separated. Some- 

 times the zoospore does not completely extricate itself from 

 the parent cell ; and it may begin to grow in this situation, the 

 root-like processes which it puts forth being extended into the 

 cavity. A true sexual generation has been observed in several 

 Confervaceffi ; and is probably universal throughout the group. 

 Thus in Sphceroplea ammlina, according to the recent observa- 

 tions of Dr. Cohn,^ the ring-like masses of endoehrome, of which 

 Several are found in each cell, resolve themselves in certain of 

 the cells into minute bodies resembling the antherozoids of 

 Chara (Fig. 112, ii), which, after moving freely within these 

 cells, escape through apertures in their walls, and then penetrate 



I See the account of these processes in the " Miorographic Dictionary," p. 468. 

 '■' •' Monatsberichte der Konigl. Akad. der Wissenschaften," Mai, 1855. 



Process of cell-multiplicalion in 

 Conferva gtomerata:—A, portion of 

 filament willi incomplete separa- 

 tion at a, and complete partition 

 at 6 i B, Itie separation completed, 

 and new cellulose partition being 

 formed at a ; c, formation of addi- 

 tional layers of cellulose wall, c, 

 I)eneath the mucous investment, 

 d, and around the primordial utri- 

 cle, a, whiclr encloses the endo- 

 ehrome, 6. 



