CHAPTER VIII. 



METABOLIC CHANGES BETWEEN PROTOPLASM, NUCLEUS, AND 

 CELL PRODUCTS. 



ALL the morphologically different parts of a living organism, 

 necessarily stand to one another in a definite relation, as regards 

 metabolic changes. In most cases it is extremely difficult to 

 understand these relations, on account of the complexity of the 

 vital processes. However, some knowledge has already been 

 gained upon the subject, by means of observation and experiment, 

 and the fact that protoplasm takes part in all formative processes, 

 such as the formation of the cell-wall, of intercellular substance, 

 etc., is indicated by various circumstances, which can scarcely be 

 explained in any other manner. 



In plants the main portion of the protoplasm is always massed 

 together at those parts, where growth is chiefly taking place : e.g. 

 at the ends of growing root-hairs, in the growing hyphae, with 

 Fungi, etc., and at the growing points of multicellular and uni- 

 cellular plants, such as Caulerpa. Further, the protoplasm, in r 

 individual cells, always accumulates in the regions of greatest i 

 activity. 



Sometime before the cellulose membrane of a plant-cell forms 

 thickenings or sculpturings, the protoplasm undergoes prepara- 

 tory changes, by collecting in the places where the most rapid y. 

 growth is taking place. Further, whilst these thickenings are 

 being formed, continuous streams of granular protoplasm are seen 

 to pass along them. 



If a small portion of Vaucheria is cut off, the protoplasm im- 

 mediately tries to repair the injury. " Granular plasma can be 

 seen to collect in dense masses about the wound, and to close up 

 to form a layer, which is sharply defined externally. A cell- 

 membrane immediately commences to develop upon this layer.'' 

 (Klebs.) 



If the protoplasm of a plant-cell has by means of plasmolysis 

 been separated from its membrane, without damage having been 



