1 tXi Fritscli . Stmlies ou t'yanophyceae. 



tu Gomuiit (loc (it. ]). 212) its clicinical Ijcliaviour is midwuy 

 between that of tlie cutiele of lii^lior plants and the membrane 

 <»i' the Fun^i, boiiiii; more resistaiit tluiii this latter. But by fnr 

 its most iin])(»rtant pcculiarity .'^ccins to ine to lie in« its great 

 elasticity, which is \vell ex<'m])lilied by Brandts (03, p. 30H) 

 recent experinients on plasniolysi.s in this grou]); according to 

 liim (p. H03) .jdeuten die Erscheinungen auf eine größere Ehisti- 

 zität der (hja)wp//gcep)i-Mem.hn\n und auf eine festere Vei'- 

 bindung zwischen ilir und dem Phisnia. Eine so vollständige 

 Ablösung des letzteren, wie solche an Grünalgen leicht erzielt 

 werden kann, kommt bei den CijanopJiyceen nur an besonders 



günstigen Oljjekten vor, In der Mehrzahl der Eälle 



folgt die Membran auf größere oder kleinere Strecken dem 

 sich kontrahierenden Plasma, und es findet oft niu' an ganz 

 kleinen, vereinzelten Stellen Ablösung statt". 



In its physical properties therefore the membrane of the 

 CyanopJiycoae is quite unlike that of other Algae. I am in- 

 clined to regard it as a modified plasmic membrane of a more 

 or less viscous mucilaginous nature and. if we choose to apply 

 to it the term cell-wall, we must keep in \'iew the fact, that it 

 differs very markedly from the structure, usuaUy so called. It 

 is probably a membrane of a rudimentary type of development 

 and we need not be surprised to find it in a group, in which 

 cytological differentiation is on so low a basis. The heterocysts 

 appear in sonie respects to have a better differentiated mem- 

 brane, but a detailed comparison with the membrane of the 

 vegetative cell is yet wanting. — I shall have occasion to men- 

 tion further examples, illustrating the elasticity and viscous 

 nature of the cellular envelope in the course of this jiaper. 



A few words must be added here on the subject of the 

 protoplasmic coimections between the individual cells in Cyano- 

 j[>]iyceae\ such connections have been described and tigm-ed by 

 a number of different authors (Borzi SQ^ p. 74, Tab. III: 

 Nadson 95, Tab. Y. fig. 55), and were especiaUy characterised 

 by their remarkable size. In the first paper of this series 

 I have myself (04. p. 93) described and figm-ed (loc. cit. fig. 3, 

 (), 1} such cases, but I am now inclined to place an entirely 

 different interpretation on them. In coirespondence with its 

 viscous character the cell -membrane will frecpiently become 

 more or less compressed or drawn out between adjacent cells. 

 which may either be merely due to mechanical strain and 

 is especially liable to be caused by the various staining reagents, 

 used by the above-mentioned investigators. Tf filaments of 

 Änabaciia for instance are stained with methyl blue^; we get 

 appearances, such as those in figs. 1 and 2. All these cases of 

 so-called protoplasmic continuity therefore are probably merely 

 due to contraction of the intercellular portion of the cellular 



') The filaments have to be retaiiied in the stain for about tvvo days to 

 produce an appi-eciable result. 



