THE ‘NON-CELLULAR’ TYPE § 53 
The whole is strongly impregnated with a 
deposit of lime, whereby the plant acquires 
a considerable degree of strength and 
rigidity. The remarkable cactus- or opuntia- 
like form is produced by a wonderful weaving 
together of the branching filaments of which 
the whole plant is made up. There are no 
traces of cross walls in these tubular branches, 
but there is a considerable difference between 
the different regions of the branches them- 
selves. The lower part of each branch 
system runs down the centre of the plant, 
while the final short twigs form the outer 
surface of the flattened segments. These 
final branchlets are closely adherent, and the 
flattened segment of the plant, looked at 
from the outside, seems to be clothed with 
a mosaic of small cells—these being, of course, 
the tips of the branches just mentioned. 
Not only this, but the chlorophyll is almost 
entirely confined to these peripheral branch- 
lets, whilst the hinder and wider parts of the 
tubes serve to store and distribute the food 
material manufactured in the tips when 
exposed to light. 
Halimeda, then, furnishes a wonderful 
example of co-ordinated growth. The singular 
completeness with which it has solved the 
problem of attaining a very high degree of 
specialisation with the simplest materials, 
extends to every detail of its structure. It 
is admirably adapted, both to utilise the light 
and to store away the material products of 
