230 VEGETABLE PHYSIOLOGY 



assimilated by the living substance. This view is sup- 

 ported by observations made upon the utilisation of the 

 reserve stores of proteids found in seeds, which have been 

 found to give rise to similar amido-acids before being 

 transported from the site of storage. To this point we 

 shall return in a subsequent chapter. 



We cannot say either in what form proteids are tem- 

 porarily stored in the cells of their first formation. Pro- 

 bably, like starch, they are made indiffusible and so retained 

 in the cell. But whether they are thrown into a solid 

 form we do not know. If so, they are amorphous and are 

 hidden away hi the substance of the protoplasm. They may 

 be kept in solution in the sap which saturates it. Different 

 forms of globulin and albumin have been found in the 

 cells in different regions. It is possible again that the 

 manufacture of proteid may be only so great as to provide 

 for the needs of the cells in which such formation takes 

 place, together with the amount that can diffuse during 

 such manufacture, so that there may be no occasion for a 

 temporary storage there. 



The translocation of food has no very determinate 

 direction. On leaving the cells which are the seats of its 

 formation, its path is dependent on physical processes 

 taking place in different parts of the plant. We can study 

 it most simply by taking a special case, which as before 

 may conveniently be that of sugar. We have seen that it 

 passes from cell to cell under the influence of osmotic 

 diffusion that is, that when two contiguous cells contain 

 sap of different degrees of concentration, an interchange of 

 the liquids takes place till the sap of both cells becomes 

 uniform. The nbro-vascular bundles, the bast of which we 

 have seen forms its principal path, extend in complete con- 

 tinuity throughout the plant, so that any travelling com- 

 pound can be transported from the leaves to the growing 

 points of the stem and root. So long as it is being used 

 by the protoplasm in these regions, the sap of the cells of 

 the tissue there, which are using it in the construction of 



