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CHAPTER II 
THE DIFFERENTIATION OF THE PLANT-BODY 
THE primary needs of a complex plant are the same as those 
of a single protoplast, the greater size of the former involv- 
ing, however, a more elaborate method of supplying them. 
In multicellular plants we consequently meet with a con- 
siderable degree of differentiation of structure. Hach proto- 
plast, which is one of the units of the colony, has originally 
the same properties as the unicellular plant. With increase 
of number in the plant-body, and with the consequent 
increase of size, a certain division of labour soon makes 
its appearance, and particular groups of cells develop one 
property more than the others. A specialisation of powers 
is very quickly apparent, and we can recognise masses of 
cells devoted to the discharge of one function, others to 
that of another, and so on. Such limitations of the powers 
and properties of the individuals have for their object the 
well-being of the community of which those individuals 
are constituents. 
Various groups of plants show this specialisation of 
function or differentiation of structure in very different 
degrees, any particular development having a special 
reference to the habitat or the mode of life which is 
characteristic of the community in question. A plant-body 
which takes the form of a long filament or a plate of cells 
shows little differentiation ‘beyond the formation of a 
vacuole in each protoplast. The setting apart of special 
cells for purposes of reproduction is generally the first 
specialisation which takes place. 
As soon as the cells of the plant begin to divide in 
é 2 
