AND ITS RELATION TO ANIMAL LIFE 1 19 



tic humus, or it may be a humus containing 

 a maximum chlorophyll, or any variation 

 between the two, which variation would be 

 capable of constituting a great chemical differ- 

 ence. 



One important point in a normal humus 

 would be that there would be a much higher 

 percentage of iron, nitrogen, and possibly other 

 mineral matter which would be in a thoroughly 

 assimilable form ; this would enable the plant 

 to take up the maximum quantity of food in 

 a given period, thus ensuring the largest yield. 



The quality of the humus is of the greatest 

 importance again, because humic acid, a pro- 

 duct of humus, plays a very important part in 

 the science of agriculture. I very much doubt 

 if its full scope is known or recognized, but 

 there is no question this acid is a solvent of 

 silica, and without going into all the chemical 

 points of the question I think it will appeal to 

 the common sense of most people that a nor- 

 mal humus will be likely to produce a much 

 more potent humic acid than will a chlorotic 

 humus. 



If this be so, it is clear that the quality of the 

 vegetable matter which is used to make humus 



