FUNCTIONAL RELATIONS OF CELL COMPONENTS 221 



groupings of the components of these substances vary sufficiently 

 to give the widest chemical, physical and physiological properties. 

 No definite information is at hand concerning the relative compo- 

 sition of the cytoplasm and the plastids lying in it. The latter 

 are probably of a denser consistency. Neither is the character 

 of the plasmatic membrane known. The cell wall is a secretion 

 product of the protoplast, and is not to be regarded as living sub- 

 stance even in its earlier stages of formation, although it is at all 

 times during the life of the cell under the control of the living 

 matter, so far as its form and structure are concerned. The wall 

 may differ widely in structure and chemical composition. It is 

 composed of a group of carbohydrates which for convenience 

 may be grouped under the term cellulose. The presence or pro- 

 portion of any of the constituents is a matter of the greatest varia- 

 tion. The wall is in a state of constant change during the life 

 of the protoplast which it encloses. Not only does the living mat- 

 ter induce changes in it but the infiltration of the material drawn 

 into the cell, and the deposition of other secretions, add to the 

 complexity of the wall which is thus seen to be a morphological 

 affair, rather than an organ of the cell. Lignification, suberization, 

 cutinization and the formation of pectates as a result of the action 

 of certain enzymes (see pectase) are the more important of such 

 changes. 



290. Functional Relations of the Cell Components. A proto- 

 plast may be regarded as a physiological, or functional unit, and 

 none of its organic components are capable of anything but limited 

 existence, and restricted action, when separated from the remainder 

 of the cell. The nucleus or fragments of cytoplasm, may live for 

 many days or even weeks, when separated from each other, and 

 many forms of metabolism may be carried on in them, but no 

 actual independence or complete action is established. Some 

 writers maintain that separated fragments of the protoplast can 

 carry on only destructively metabolic processes and the functions 

 connected with them, but this is not confirmed by all of the facts. 

 Thus the synthesis of carbohydrates is accomplished by separated 



