70 PLANT LIFE 



and diffusible sugar, travels in the latter form 

 to other parts of the plant. It passes to the 

 growing regions, where it is utilised in growth 

 processes, to storage tissues where it is re- 

 converted into starch or into some other food 

 reserve, or it is drawn towards any other centre 

 of activity where a consumption of carbo- 

 hydrate is in progress. 



We have learned in a former chapter that 

 water plays an important part in photo- 

 synthetic production of carbohydrate. It 

 not only acts as a physical agent, by main- 

 taining the protoplasm in that state of watery 

 consistence essential to chemical change, but 

 it also forms part of the raw material which 

 enters into the actual composition of the 

 sugars and similar substances. Furthermore it 

 serves as the vehicle by which salts containing 

 phosphorus, sulphur and other substances 

 which enter into the composition of proto- 

 plasm, or are essential to its proper working, 

 can enter the plant from without. The excess 

 of water is eliminated from the plant by the 

 diffusion or transpiration of the watery vapour 

 through the stomata. 



