Studies on ('tj(niopliijce(te. 



F. E. Fritsch, B. Sc, Pli. D., F. I.. S. 



University College, London. 



II. Structiire of the investmeiit and siMjre-developmeut in some 



Cyan oplii/ceae. 



(With Plate VII.) 



1. General remarks. 



In tlie course of tlie examination of stained filaments of tlie 

 Anabaena^ whicli formecl tlie subject of tlie tirst paper of this 

 series (Fritscli 04), niy attention was attracted by the cnrion.'^ 

 structure, presented by the immediate cellular Investment. The 

 detailed structure seemed to indicate, that the cells of a filament 

 of Anahaena retain their individuality to a greater extent, thaii 

 appears at iii'st, and althougli this structure is most emphasized 

 in filaments. which are proceeding to form spores. it occurs also 

 in the pui'ely vegetative stage. A number of further genera of 

 Cyanojjinjccac were examined and the interpretation of the 

 features tliere observed in the light of those, discovered in 

 AnahaoHü, leads to some interesting comparisons; a large number 

 of genera still remain univestigated , but I liave piu-])osely 

 omitted the more elaborate heterocystous forms for the present. 



The immediate Investment of the Cyanopliyceous cell has 

 reeeived httle attention and those, who have examined it, came 

 to very' varying results. Like the cell-contents the cellular 

 envelope of the blue-green Algae differs very markedly from 

 the same structure in other Algae. In the first place (and this 

 applies to Anahaena amongst others) it is offen extremely dif- 

 ficult to recognise in the unstained vegetative condition. This 

 led some observers such as Kützing (43, p. 48 and 180) and 

 Borzi (86, p. 82j to consider, that the protoplast was merely 

 bounded by a plasmic membrane in most cases; thus within the 

 mucilaginous Investment of a Nodoc Borzi distinguishes a 

 further enveloj)e ('parete"), but this is regarded as being merely 

 a peripheral portion of the protoplasm ('tutto inseparabile dal 



