43 8 Acton.— Observations on the Cytology of the Chroococcaceae. 
Brilliant blue and Bismarck brown were used for the identification 
of cyanophycin granules and central granules respectively. Unfortunately, 
brilliant blue stains everything in the cell, and it was found best not to 
overstain to bring out the cyanophycin granules. 
IV. The Protoplast of Chroococcus Turgidus (Kutz.), Nag. 
Although Chroococcus macrococcus is perhaps the most interesting 
member of the Chroococcaceae, it cannot be considered as typical of the 
group. Also it is impossible to discuss . its systematic position without 
comparing its cytology with that of other members, so that it will be 
described separately at the end of this paper. 
Chroococcus turgidus was examined in great detail, and as the structure 
of the protoplast in this plant appears to agree almost entirely with that of 
the remaining species except Merismopedia elegans , I propose to first 
describe fully Chroococcus turgidus , and then to deal with any facts of 
interest in connexion with other species. 
Among the literature on the Cyanophyceae there only appear to 
be three papers mentioning Chroococcus turgidus as one of the species 
examined. 
Palla (’93) makes special mention of it only with regard to the 
cyanophycin granules, the presence of which he was unable to demonstrate. 
Nadson (’95) worked at several unicellular species, among which was 
Chr. turgidus . His conclusions were briefly as follows : The protoplast 
shows an alveolar structure in the sense of Biitschli, and the outer portion 
functions both as cytoplasm and chromatophore. The pigmentless inner 
portion is only distinguishable from the outer portion by the fact that 
it contains a more strongly staining substance, and that in this region 
the so-called chromatin granules (metachromatin granules) are exclusively 
or especially concentrated. There are three kind of granules in the cell- 
chromatin granules (metachromatin granules), reserve granules, and plas- 
matic microsomes. The latter are only found in Merismopedia and 
Aplianocapsa. They are small granules of plasmatic substance occurring at 
the junctions of the meshes of the alveolar protoplasm. The chromatin 
granules are especially, but not exclusively, concentrated in the central 
body, and are variously distributed in different species. The reserve 
granules are situated in the peripheral portion of the protoplasm. Division 
is usually direct. 
Lastly, Chodat (’96) has a special paper on Chroococcus turgidus. He 
fails to find a definite nucleus. The central portion is quite often coloured 
in addition to the peripheral portion, and there can be no reason therefore 
to distinguish a special chromatophore. Mucilages, soluble amides, and 
cyanophycin can appear in the protoplast. The distribution of these sub- 
stances varies exceedingly according to physical conditions, but they may 
