222 CHEMISTRY OF PLANT LIFE 



has a definite structure, composed of (a) a nucleus; (6) numerous 

 granular bodies of different sizes and kinds; and (c) a clear mass of 

 colloidal material, which (if observed under the ultra-microscope, 

 or photographed by ultra-violet light) is apparently made up of 

 very minute particles of many different types of materials; 

 the whole mass, in the case of plant protoplasm, being generally 

 surrounded by (d) a differentiated layer known as the cell-wall. 

 The actual internal structural arrangement of the clear colloidal 

 mass is uncertain; but its properties indicate that it may be con- 

 sidered to be like a mass of foam (resembling a compact mass 

 of soap-bubbles) the compartments of the foam being, of course, 

 very minute and the films themselves almost infinitely thin, the 

 contents of each compartment being probably liquid, and the 

 whole composing a typical colloidal gel of complex composition. 



This conception may not be accurate in every detail, but it 

 seems to fit very closely the conditions and reactions of cell proto- 

 plasm. Furthermore, it is obvious that the definite structure, or 

 form, of the cell is essential to its life; since, if the structure be 

 destroyed by any kind of mechanical injury (freezing of the cell 

 contents, resulting in the puncturing of the membranes by ice 

 crystals; rupturing of the films, or cell-walls, by grinding with 

 sharp sand, etc.) so as to bring about an intermingling of the parts 

 which are segregated from each other in the organized structure, 

 there results an immediate exhibition of abnormal chemical actions, 

 accompanied by the liberation of carbon dioxide, and the death of 

 the cell. 



A proper mental picture of the organization of the cell structure 

 and of the interrelation of all its working parts is suggested by the 

 figure of a well-organized chemical factory, with the different 

 chemical transformations which are involved in the whole process 

 being carried on in different portions, or rooms, of the factory, 

 with the various intermediate and final products regularly and 

 systematically transported from one room to another as they are 

 needed to keep each individual step in the whole process going at 

 the proper rate, and with the different parts of the whole factory 

 working in smooth coordination with each other. Any disturb- 

 ance of the mechanism in any particular room, or any abnormal 

 condition which breaks down the coordination or results in the 

 mixing of the reagents or processes of adjoining rooms in improper 

 order or proportions, produces instant destruction of the normal 



