470 
Carter .— The Cytology of the Cladophoraceae. 
Where the cell-contents are not quite so profuse, however, this external 
layer is often more or less perforated, so that considerable patches of the cell- 
wall are left uncovered (PI. XXVII, Fig. 3). In Text-fig. 1, C, a segment of 
this kind is seen in section, and it is quite clear that the chloroplast does not 
Text-fig. i. Rhizoclonium hieroglyphicum-, .(KWtz.) Stockm. a, transverse section of a fila- 
ment in the autumn condition ; B, external view of part of a similar filament ; C and D, transverse 
sections of a very narrow form ; E and F, transverse sections of a much larger form ; G, part of 
a longitudinal section of a similar filament ; st , starch-grains. All x 910. 
cover the whole cell-walk The size of the perforations depends entirely on 
the amount of chloroplast available in the particular segment, and therefore 
often varies in different parts of the same thallus. This is particularly 
noticeable in Cladophora glomerata, (L.) Kiitz., in which the younger apical 
segments are often densely filled with cell-contents, and here the cell-wall 
is usually completely mantled by the chloroplast, whilst in the lower cells 
