44, PLANT LIFE 
the slippery gelatinous character of its mem- 
branes. The cells of the filaments are com- 
monly elongated, but each one behaves very 
much as an independent unit. The effect of 
one cell upon another is of the slightest under 
ordinary circumstances. Each divides trans- 
versely, and so multiplies, independently of 
its neighbours. The filament thus grows in 
length, but it usually has no distinguishable 
base or apex, nor does it branch. Altogether 
the organising effect of the cell union is as 
yet of the very simplest kind. 
Another common alga, Cladophora, presents 
quite a different state of affairs (Fig. 6). This 
plant, like the foregoing, consists of cells placed 
end to end, but there the similarity ceases. 
Each cell is definitely part of the organism. 
The filament is attached by a specialised basal 
cell and it increases in length solely by trans- 
verse division of the apical cell. Branches 
may spring from the cells behind the apex, 
and they then commonly appear in regular 
sequence, the youngest branches arising as 
outgrowths from the anterior (e. g. nearer the 
growing point of the stem) end of the cell 
nearest the apex. 
Not only, therefore, is the plant as a whole 
organised in such a way that there is a base, 
as distinct from an apex, but this distinction 
is also impressed on every cell! which helps 
1 In a certain sense the expression “cell” is not 
appropriate to the structural unit of Cladophora, since 
each “ cell” really represents a syncytium (p. 21) because 
its protoplasm contains several nuclei. 
