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Carter . — The Cytology of the Cladophoraceae. 
Brand (1898) considers the question of the number of nuclei in the 
Cladophoraceae and comes to the conclusion that it is not the character of 
the genus and the length of the cells which are important in this respect, 
as was formerly believed, so much as the cubical content of the cell. In 
a later work Brand (1909 B) points out that in certain conditions, for 
example in the ‘ statu subsimplex certain thin varieties of Cladophora may 
only have one or few nuclei in each segment, so that the number of nuclei 
cannot be used as a systematic distinction between the two genera 
Rhipocloniitm and Cladophora. 
Thus the cytology of the larger members of the Cladophoraceae has 
not been thoroughly investigated and there has long been some doubt with 
regard to their exact nature. The statements of Schmitz (1879, 1882) 
and Kjellmann (1897) that the chloroplast is not confined to the parietal 
positions but also penetrates into the interior of the cell have been doubted 
by Brand (1901, 1902), and it was felt that the only means of obtaining 
accurate information was by cutting sections. Professor G. S. West therefore 
suggested that this work should be undertaken. 
Methods . For the Cladophoraceae the best fixing solution was found 
to be corrosive sublimate, 3 grm., glacial acetic acid, 1 c.c., and 50 per cent, 
alcohol, 100 c.c. The solution was used cold, and was allowed to act for 
about 30 seconds. The solution used for the fixing of Desmids, which was 
exactly similar but contained 3 per cent, acetic acid, was found to have 
a too violent action on the cell-wall for it to be satisfactory in the case of 
Cladophora ; cf. Brand (1901). The subsequent treatment was similar to 
that used in the case of Desmids . 1 
Some of the material was embedded in paraffin and sectioned, since, 
owing to the large size of the cells and the dense nature of the cell-contents, 
particularly in the autumn condition when starch is accumulated in large 
quantities, it is quite impossible to come to any conclusion about their 
structure from mere superficial observation. 
Cytology. 
The algae examined were freshwater species of Chaetomorpha , Rhizo- 
clonium , and Cladophora , since only these were available. 
The cytology of these genera was found to be quite similar, although 
the exact condition of the segments was liable to variation according to the 
relative profuseness of the cell-contents. 
The chloroplast invariably consists of an extensive parietal sheath 
mantling the whole cell-wall, including the transverse septa, and which in 
segments with plentiful contents forms an almost uninterrupted layer 
(Text-fig. 1 , B). 
1 Carter, N. : Studies on the Chloroplasts of Desmids. I. Ann. Bot., xxxiii, 1919. 
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