F r i t s c li , Stiidies on CVaiiupliy ceae. 201 



stuclied, — a point of difference froiu the cases, described by 

 Borzi (cf. p. 33). The latter autlior does not describe the way, 

 in which the two walls of" the spore develop in Äiiabaeua. I 

 leave a further discussion of the spore and its rehition to the 

 „gonidia'' of Brand (03, p. 44 et. seq.) to the next paper of 

 this series ^). 



In the examination of well-advanced sporogenous filaments 

 numerons stages are met with (hg. 7, 8), whieh seem to me to 

 quite phiinly support the theoiy of structure of the investment. 

 propounded in the preceding pages. Specimens, such as that 

 represented in fig. 8 are of quite common occurrence; here the 

 uppermost spore is about to Hberate its contents and the ter- 

 minal (transverse) portion of the inner investment is more or 

 les.s papillosely developed on one side and this papilla quite 

 visibly protrudes through the open end of the cell-sheath. 

 Again in hg. 7, which represents the contents of a sporogenous 

 cell in course of protrusion, one end of the cylindrical cell- 

 sheath quite vi.^ibly surrounds the equator of the protoplast, 

 which is enveloped in a new inner investment. Such cases will 

 be further discussed in the third paper of this series. 



I still wish to add a few words on the behaviour of the 

 external mucilaginous investment of the Anahaena towards stains. 

 Treated with Vesuvin it turns brown and is seen to consist of 

 a number of successive layers. The innermost, and therefore 

 most recent, of these closely follows the outline of the cell- 

 sheaths of the individual protoplasts and thus presents a monili- 

 form appearance, indicating the excretive activity of each cell. 

 These Investments do not include the heterocysts (cf. Brand 

 03. p. 44). It is very instructive to watch the behaviour of a 

 hlament, wlien Vesuvin is slowly added under the microscope. 

 A very wido mucilaginous investment, which was quite invisible 

 before, becomcs indicated by its margiijs contracting slightly 

 and taking on the brown stain. The contraction goes on very 

 slowly but evidently, and at the same time the mucÜage acquires 

 a darker and darker brown colour; ultimately it encloses the 

 hlament as (juite a narrow shoath, showing one or more layers 

 of stratihcation. In all probabiUty many of the layers discer- 

 nible during the process of contraction are due to folds. As 

 soon as any cell of a Hlament becomes transformed into a 

 ln'terocyst excretion of mucilage from this cell ceases and the 

 stratitication of the mucilaginous envelope seems in the main to 



^) The spores of certain Cyanopliyvcae (e. g. Nosfor nilcroscopicum Carm. 

 N. commune Vaiich., Gloeocapsa alpina Näg.) differ in tlio lack of au exo- 

 spore, wliicdi is i'eplacpd by a tliick and coiisistent nuicilage sheatli (cf. 

 Brand 03, p. 85, 86). These are all aerial species. These forms are inter- 

 esting. as to my tliinking they show. that in certain cases the spore does 

 not deveh)!) a special cell-sheath (whicli is rcgarded as a modified innermost 

 layer of the external mncilage), but that this structure is replaced bj' the 

 whole of the outer mucilage becoming more consistent, — a pure case of 

 homology. 



