21 
many generations, perhaps not more than 7' 3, and the humus 
has been formed largely under humid or semihumid conditio 
It is probable that oxidation takes place more actively in arid than 
in humid soils, which oxidation probably results hi a greater degi • 
decomposition of the nonnitrogen constituents, thus leaving a humus 
residue richer in nitrogen. Also, the humus may be considered as 
being older than that occurring in humid soils, for the reason that 
greater amounts of plant residues are continually becoming incorpo- 
rated with the soils under conditions that are more favorable for plant 
growth, such as are offered by a more abundant moisture supply. 
For these reasons (perhaps others) it is to be expected that the humus 
of arid soils would be more largely composed of nitrogen constituents 
than that of humid soils. 
STTMMAKY. 
(1) The nitrate and ammonia content of Hawaiian soils constitutes 
only a small percentage of the total soil nitrogen. 
(2) Upon boiling different soils with strong hydrochloric acid, the 
amounts of nitrogen dissolved ranged from 67.51 per cent to 91. 8S per 
cent of the total nitrogen. With two exceptions, the relative per- 
centages of amid nitrogen, split off in the hydrolysis, were approxi- 
mately the same, amounting on the average to 23.91 per cent of the 
nitrogen dissolved. Basic nitrogen occurred in the solutions in vari- 
able amounts, the average being 9.98 per cent of the soluble nitrogen. 
The percentages of nonbasic nitrogen, determined by difference, 
proved to be quite concordant in most of the soils, amounting on the 
average to 64.57 per cent of the soluble nitrogen. 
(3) The relative percentages of amid and basic nitrogen, split off 
in the hydrolysis of Hawaiian soils, stand in the reverse order to that 
in which they occur in the vegetable proteins; while the percentage of 
nonbasic nitrogen practically equals that found in the vegetable pro- 
teins. It had been suggested that soil bacteria attack the nitrogen 
bodies in such way as to split off the basic nitrogen compounds, and 
that these then become ammonified, or otherwise lose their identity 
as di amino acid compounds, possibly being partially converted into 
amid forms. 
(4) Anaerobic conditions predominate in Hawaiian soils, and under 
such conditions the nitrogen is more soluble than in well aerated - 
but the relative percentages of the different groups of organic nitr _ 
compounds seemed not to be affected by the predominance of ofl 
the other of these conditions. 
(5) The amount of nitrogen soluble in 1 per cent hydrochloric acid 
was about twice a- large a- that of amnion:; 3 ally occurring in 
the soil-. 
