LUTHER BURBANK 



of a number of minerals; notably compounds of 

 phosphorus and potash and lime, but including 

 six or eight others that must be present in in- 

 finitesimal amounts. 



And the building of these substances into 

 combination with the sugar in such a way as to 

 produce the substance called protoplasm, the basis 

 of all life, constitutes the culminating stage of the 

 miracle. But the way in which this is effected is 

 even less clearly understood. 



We do know, however, that all these substances 

 are brought to the plant in watery solution. 



Nitrogen constitutes about four-fifths of the 

 atmosphere, as everyone knows, and hence it 

 seems rather strange that the plant does not draw 

 what nitrogen it needs from this source, in par- 

 ticular since it gets its carbon from the air. 



But in point of fact the plant, no less than the 

 animal, might starve to death from lack of nitrogen 

 even while its tissues are everywhere bathed in 

 nitrogen gas. To make the nitrogen available for 

 the purpose of nutrition it must be made into 

 soluble compounds called nitrates, and must be 

 supplied in dilute watery solution. 



Such nitrates, therefore, are among the most 

 important of the soluble compounds that must be 

 contained in the medium surrounding the roots of 

 the plant. Sucked up by the rootlets in dilute 



[34] 



