474 Carter. — The Cytology of the Cladophoraceae. 
more or less reticulated parietal film. The nuclei were in this form of very 
large size in comparison with the small diameter of the cell, and therefore 
projected considerably from the thin parietal film of chloroplast into the 
cell-cavity. Thus they were usually not entirely immersed in the chloro- 
plast (Text-fig. i, c and d). 
In a rather thicker form examined the condition approached more 
nearly that found in certain forms of Cladophora (Text-fig. i, E-G). 
The projecting of the nuclei into the cell-cavity is often observed in 
some forms of Cladophora and Chaetomorpha in which the lining parietal 
film of chloroplast is extremely thin (Figs. 4 and 5 ; Text-fig. 2), but this is 
far more pronounced in the narrow form of Rhizoclonium hieroglyphicum 
described above. 
With regard to the number of nuclei occurring in the segments of 
Rhizoclonium hieroglyphicum , the narrower form very often had only two, 
although four and eight were also very frequent, whilst in some very well- 
nourished filaments, the cells of which had very dense cell-contents, the 
nuclei were often as many as sixteen. In the larger form the nuclei were 
always more numerous (Text-fig. 1 , G), eighteen to twenty-four being com- 
monly found in segments of medium size. In opposition to this it was 
noticed that in Cladophora crispata , (Roth) Kiitz., the nuclei in many of the 
segments having very scanty cell-contents were very reduced in number, 
sometimes to eight or nine. 
These observations tend to support those of Brand (1898), that the 
number of nuclei depends not on the genus itself but largely on the cubical 
content of the cell, and also show that the relative abundance of the cyto 
plasmic contents of the segment also plays some part in this respect. 
Both Rhizoclonium and Cladophora accumulate large quantities of starch 
during the autumn months of the year, and material was therefore examined 
in this condition in order to get exact details of its storage. In the external 
view the parietal film of chloroplast is usually seen to be quite continuous, 
and its protoplasmic reticulum is very coarse, the cavities between the 
meshes being occupied by innumerable starch-grains (Text-fig. 1 , B). 
Thus the whole of the chloroplast between the pyrenoids is densely 
packed with starch-grains, and these also extend into the films of chloro- 
plast between the nuclei and the cell-wall, so that the nuclei are often 
pushed farther into the interior of the cell. This is better seen in sections 
(Fig. 2; Text-fig. 1, a). 
The strands of chloroplast traversing the lumen of the cell are similarly 
packed with starch, and become very distended, occupying even more of 
the cell-cavity. In this condition no trace of colourless cytoplasm can be 
detected, and the nuclei are even more completely enveloped by the 
chloroplast (Figs. 2 and 7 ; Text-fig. 1, A). 
In Rhizoclonium the cell becomes nearly solid with pyrenoids and starch, 
