CHAPTER VIII. 

 THE STORAGE SYSTEM. 



I. GENERAL CONSIDERATIONS. 



As a general rule, synthetic products employing the term in its 

 widest sense are not made use of by the plant immediately after their 

 formation. Even in the case of substances that are destined to be 

 used up by the cells in which they are manufactured, consumption does 

 not usually follow hard upon production. For the internal and ex- 

 ternal conditions controlling the activity of synthetic processes are by 

 no means identical with the factors determining the utilisation of 

 the product of synthesis, among which " growth " holds a prominent 

 place; consequently a more or less extensive interval of time almost 

 always intervenes between the production of plastic materials and 

 their consumption. This fact may be readily verified even among simple 

 filamentous Algae, such as Spirogyra or Ulothrias, which are photo- 

 synthetically active in the daytime, and undergo cell-division at night : 

 evidently the plastic materials synthesised by day with the aid of sun- 

 light, are used up during the night in the formation of new cell- walls, 

 or in other ways. Among the Higher Plants the condition of affairs is 

 naturally more complicated. Here manufacture and consumption take 

 place not only at different times, but also at different places. Now, it 

 is the separation of these two processes in space that necessitates the 

 translocation of synthetic products : similarly, their separation in time 

 entails storage of these substances on a more or less extensive scale. 



The greatest possible variety prevails with regard to the parts of 

 the plant-body that are utilised for storage. The simplest plan con- 

 sists in the deposition of plastic material at the place where it is 

 formed: this condition is exemplified by the production of starch-grains 

 in the interior of chloroplasts. In other instances the plastic sub- 

 stances are deposited, at points far removed from their places of origin. 

 in cells of the most varied kind, including bast-fibres, certain elements 



