NUTRITION OF PLANTS. 355 



on the fulfilment of which the most momentous 

 results to all animate creation depend. 



In a previous section of this work it was 

 stated that plants derive but a small proportion 

 of their solid constituents from the soil in 

 which they grow. It has been before men- 

 tioned that the chief solid material of a plant 

 is its carbon ; also that plants live with their 

 roots buried in a material (vegetable mould) 

 extremely rich in carbon. Yet, on the ques- 

 tion being put, Do plants derive their carbon 

 from the mould? the answer has been, Certainly 

 not. This must now be proved. 



Experiment has shown that it is impossible 

 for a plant to receive nutriment by its roots in 

 any other but a soluble and perhaps a gaseous 

 form. Be the nutrient material what it may, 

 it must first be in one or other of these con- 

 ditions, before it can be appropriated by the 

 vegetable economy. The rootlets cannot take 

 up solid matter ; nor, if they could, could the 

 plant grow upon such a diet. If the hungry 

 fibres wandered in their search for food through 

 a mass of dry sawdust, or threaded their way 

 through a pile of stones, they would find none, 

 because they would find nothing dissolved 

 in such a situation. 



Applying this to our present subject, vege- 

 table mould may be considered as almost in- 



