THE VEGETABLE CELL. 



lis 



Fig, 49. 



out into a more or less flat disk (tlie thecal layer) ; in the covered- 

 fruited, it remains enclosed in the thallus. In each of the parent- 

 cells eight spores are formed by free cell formation, and in very 

 many cases these form two, four or a greater number of secondary 

 cells in their interior. Very few observations' have been made on 

 the germination of these spores According to HoUe (" ZurEnt- 

 wlckeliingsg, von Borrera ciliaris/' — On the development of 5. 

 ciliaris, Diss. 1848, Gottingen), the secondary cells break through 

 the primary spore cell as filaments, and are con- 

 verted into cells outside the spore. According to 

 Meyer's account (" Nebenstunden mein. Beschaftig- 

 ung/' 175), the outer membrane of the spore is not 

 torn, and when a number of spores germinate side 

 by side, the filaments into which they grow out be- 

 come blended together, and contribute jointly to the 

 formation of a new plant. 



According to the observations of Tulasne (" Vln- 

 stitut," No 849), the inner spore-coat, both of simple 

 and compound spores, grows out into one or more 

 filaments, which soon ramify and acquire septa, 

 and whose short interlacing branches form little 

 cushions, upon which little colourless cells accumu- 

 late, and in which the green cells forming the rudi- 

 ments of the cortical layer of the new plant, make 

 their appearance. 



We meet with a far greater complication of phe- 

 nomena when we look towards the spores of the Algse, 

 even though here no co-operation of two sexes occurs. 

 This latter may indeed seem doubtful in a number 

 of Algas, in wliich a so-called coagulation occurs, but 

 a more minute examination of this process shews 

 that it bears no analogy to sexual reproduction. 

 This conjugation presents itself most distinctly in the 

 so-called GonjugatOB (the genera — Zygnema^ fig. 49, two ceiis of zy^^ 

 — Tyndaridea, Mougeotia, Staurocarpus, &c.), in of'^Z^u^lml^ 

 which it was observed first by Vaucher, The fila- ^j wS^foSfon 

 ments of these Confervse lie parallel, side by side, <>f t^e conneotrngr 



1 , . . ^ '^^ in branch ; b, con- 



or bent m a ziz-zag manner towards each other, n«ctrogTbwxch;c^ 

 and send out from their cell-walls towards the ^^^^^' 

 the nearest cell of the neighbouring filament, a blunt branch (a), 

 which grows together with a similar and corresponding branch of 

 the other cell coming to meet it, upon which the paitition in the 

 cross-branch (b) becomes absorbed, and the solid matter of the 

 contents of both cells becomes balled together into a mass in the 

 cavity of one of them, or in the connecting branch, this mass ac- 

 quiring a cellulose membrane, and in this way being converted 

 into a spore (c). The following circumstances tell against this 

 process being considered as an act of impregnation. The contents 



I 



