Feb., 1919] Nitrogen Content of Volcanic Ash 221 



there was nothing like sufficient total nitrogen, much less water 

 soluble nitrogen, present in the ash for the sustenance of the 

 plants. Here we have Hellriegel's famous pot experiments 

 carried out by Nature in the field on an extensive scale. Culti- 

 vated soils seldom have less than 100 parts per 100,000 of total 

 nitrogen in the surface foot. Here the total nitrogen content 

 was less than one per cent, of this amount, and the water soluble 

 ammonia and nitrite content almost nil. The presence of 

 healthy lupines growing far out on this ash flat clearly indicates 

 that all of the essential plant constituents were present in the 

 soil, while the absence of all other varieties of plants pointed to 



Photograph by R. F. Griggs 



THE PUMICE FLAT ON WHICH LUPINES ARE STARTING. 



The dark spots right and left are lupine plants similar to that shown close up on 



the opposite page. The entire absence of all other vegetation 



is very striking. 



the lack of some essential constituent of plant growth. This 

 essential was no doubt nitrogen. The lupines were doubtless 

 provided with their necessary nitrogen by symbiotic, relations 

 with the nitrifying bacteria in the nodules. 



The first four determinations in Table IV show that the 

 growing plants have not altered the ammonia and nitrous 

 nitrogen content of the ash. Those determinations on the 

 original black soil, where plants were growing in profusion, 

 indicated almost the complete absorption of all the ammonia 



