54 PLANT LIFE 
photosynthesis; whilst it has overcome the 
disabilities apparently inherent in its type 
of organisation, by strengthening and cement- 
ing together the branching filaments, of which 
it is built up, by means of the calcium car- 
bonate which it withdraws from the sea-water. 
The consideration of the noncellular or 
syncytial plant has been introduced in order 
to illustrate the varieties of one possible 
type of structure. Save, however, for the 
production of a few aquatic representatives 
it does not mark a line of important advance. 
The multicellular condition contained within 
itself the promise of the future, and it is as 
multicellular organisms that the higher plants 
have been evolved. 
It will be useful at this point to sum up the 
salient points of the preceding discussion, 
so as to gain a clear starting-point from which 
to study the evolution and modification of 
form and structure in the higher terrestrial 
forms of life. 
We have seen the striking consequences 
which accrue from the possession of an invest- 
ing membrane in their effects upon the mode of 
nutrition, and indirectly upon other functions, 
e. g. that of motility, in plants. We have learnt 
in the relatively lowly members of the vege- 
table kingdom which have been passed under 
review, why a need for the presentation of 
the green surfaces to light should be a matter 
of such cardinal importance as to dominate 
the organisation of every one of them. We 
