196 
Fritsch, Studies 011 Cyaiiophyceae. 
to Gromont (loc. eit. p. 212) its Chemical beliaviour is midway 
between that of the cuticle of higher plants and the membrane 
of the Fungi, being more resistant than this latter. But by far 
its most important peculiarity seems to me to lie in its great 
elasticity, which is well exemplified by Brand's (03, p. 303) 
recent experiments on plasmolysis in this group; according to 
liim (p. 303) .. deuten die Erscheinungen auf eine gröbere Elasti¬ 
zität der CyanopJigceen-luLemb ran und auf eine festere Ver¬ 
bindung zwischen ihr und dem Plasma. Eine so vollständige 
Ablösung des letzteren, wie solche an Grünalgen leicht erzielt 
werden kann, kommt bei den Cyano'phyceen nur an besonders 
günstigen Objekten vor,. In der Mehrzahl der Fälle 
folgt die Membran auf größere oder kleinere Strecken dem 
sich kontrahierenden Plasma, und es findet oft nur an ganz 
kleinen, vereinzelten Stellen Ablösung statt“. 
In its physical properties therefore the membrane of the 
CyanopJiyceae is cpiite 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 clioose to apply 
to it the term cell-walJ, we must keep in view the fact, tliat it 
differs very markedw from tlie structure, usually so called. It 
is prob ab ly a membrane of a rudimentary type of development 
and Ave need not be surprised to find it in a group, in which 
cytological differentiation is on so low a basis. The heterocysts 
appear in some respects to ha\ r e a better differentiated mem¬ 
brane, but a detailed comparison with the membrane of the 
A r egetative cell is yet Avanting. — I shall have oocasion to men- 
tion furt.lier examples, illustrating the elasticity and viscous 
nature of the cellular envelope in the course of this paper. 
A few Avords must be added here on the subject of the 
protoplasmic connections betAveen the individual cells in Cycino- 
phyceae ; such connections have been described and figured by 
a number of different authors (Borzi 86, p. 74, Tab. III; 
hTadson 95, Tab. V, fig. 55), and were especially characterised 
by their remarkable size. In the first paper of this series 
I have myself (04, p. 93) described and figured (loc. cit. fig. 3. 
6, 7) such cases, but I am now inclined to place an entirelv 
different Interpretation on them. In coirespondence with its 
viscous character the cell - membrane will frequently becorne 
more or less compressed or drawn out betAveen adjacent cells. 
which may eitlier be merely due to mechanical strain and 
is especially liable to be caused by the various staining reagents, 
used by the above-mentioned investigators. If filaments of 
Anabaena for instance are stained with methyl blue 1 ) Ave 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 
b The filaments have to he retained in the stain for about two days to 
produce an appreciable result. 
