2 
22 T. L. Lyon anp J. K. WILson 
could be transferred to the nutrient solution except thru the roots, as 
the seed did not come in contact with the solution at any time. 
The data for this experiment are presented in table 1. The figures 
give some definite information regarding the presence of organic nitrogen 
in the substratum in which these plants grew and which contained only 
inorganic nitrogen at the time when the young plants wereset out. Of the | 
plants used — oats, peas, maize, and vetch — all liberated organic nitrogen, 
which was found both in the solution and in the deposit at the bottom of | 
the flasks. The quantity of organic nitrogen in the solution was always 
several times as much as that in the deposit. 
The organic nitrogen in the deposit at the bottom of the flasks is 
probably the result of sloughing off of the root cells, as is indicated by the | 
presence of plates of cells in the deposit. It is possible also that a part, 
at least, of the nitrogen in solution is liberated from the plant cells in 
the same way. There is no direct evidence that the nitrogenous matter 
is liberated in any other way, but it is perhaps questionable whether the © 
quantity found in solution, especially during the early stages of growth, 
could all have come from detached cells. That these cells are alive and 
remain so for a considerable time has been noted by Knudson (1919). 
Organic nitrogen appeared in the solution before the nitrates were all | 
removed. It is evident that organic nitrogen is hberated by these plants | 
in the early stages of their growth and not exclusively at the period between | 
full bloom and maturity. That only the loss of nitrogen in later growth | 
was noticed in the field experiments previously reviewed was doubtless 
due to the fact that the plants were absorbing little nitrogen at that 
stage and were liberating it more rapidly than they were absorbing it. | 
The quantity of organic nitrogen liberated under field conditions may | 
not correspond to that obtained in these experiments, as under the con- 
ditions of the experiments there was no removal of organic matter by 
organisms other than the plant, while in the field there would presumably 
be conversion of the organic nitrogen into ammonia and nitrates. 
The pea plant that grew in a solution without the addition of combined 
nitrogen, liberated organic nitrogen into the solution in which it grew. 
The growth was by no means as vigorous as that of the pea plant which | 
was furnished with nitrate nitrogen, and the plant itself contained only | 
about one-fifth as much nitrogen as did the other pea plant, but it liberated 
more than half as much organic nitrogen. 
