•2U) 



Fritsrli. Studies on Cyauopliyceae. 



slioi-t rows of rolls ot" SipicchococcKs otlienirse recnll OsrilJaria to 

 ;i great ext eilt. 



Dangeard (99) in liis exceedingly instnictive paper on tho 

 ovolution of sexuality has shown conclusively, that the filament 

 or row of cells is tlie niost advantageons from tho nutritive 

 ])oint of view; and quite in eorrespondence with this we find 

 that in the Cijaiioplnjceae , as in other algal phyla, the filament 

 is the most successful form. The cell-sheath, which in Gloeo- 

 capsa and other nnicoUuhir forms, constitutes a firm investment 

 around the whole cell, is only necessary laterally, when the fila- 

 mentous stage is attained. By the rapid succession of divisions 

 all in one direction no time is given for the closure of the gap, 

 left in the cell-sheath, whilst by a suppression of the mucilage, 

 excreted between the products of division, a consistent trans- 



Rivulaiia 



ToUjpofhrix 



-^ 



d 

 o 



0) 



<D 

 Ü 



rd 

 Ü 



Ca 



•5 



09 



O 



Anabaena (J\ ostoc) 



TjijiKihiia 



n 



OsciUaria 



Gloeof/iece 



\ 



Gloeocapsa 



Merismopedia 



Syneehococcus 



AplKiiiofhcvv 



2 



r. 



P 



Aphanocapsa 



verse septiim originates, which completely replaces the cell- 

 sheath at this point. In this way the state of affairs, occurring 

 in Ä)iahae}ta j is attained. It should be noted that each cell of 

 the filament still retains its individuality to some extent, in so 

 far as it has its own peculiar cell-sheath, probably excreted 

 primarily by each individual cell, and, in so far as in the 

 coui'se of division of a cell, already provided with such a cell- 

 sheath, the latter is split into two portions, appertaining to the 

 daughter-cells. It seems probable that this Splitting is merely 

 due to the relatively strong development of the intercellular 

 septmn, which is certainly more strongly developed here than 

 in a form like OsciUaria, — a point of resemblance to GIopo- 

 rapsa etc. 



