The Fixation of Nitrogen. 77 
exists in our soils which only awaits the occurrence of some 
optimum condition for its excessive development. One of the 
factors in this optimum condition is an ample and continuous 
supply of moisture. 
The question of the influnece of the character of the soil has 
been frequently raised since the publication of Bulletin 155. The 
wet condition of two of the soils described in that bulletin tended 
to leave the impression that the whole trouble might be due to 
water, especially in the minds of readers who might consider the 
wet, muddy condition of the soil the only cause for the death of 
the trees, and not to consider this condition itself as the result of 
conditions other than the presence of water. It was distinctly and 
repeatedly stated in Bulletin 155 that the water in these cases was 
not free so as to form a water table at depths of six to six and a 
half feet. In the case of Orchard No. 3, I stated that the land 
where the sample of mealy, surface soil was taken was sandy and 
that the ground was only fairly moist at a depth of six feet. In 
Cases 5, 7, 8 and 9 we again have sandy and in part light clayey 
loam with sandy subsoils, and no excess of water at depths reached 
by the roots of the trees. In the Cases of Nos. 8 and 9 we have 
excellent drainage. In these cases, especially in the latter, the 
trouble can in no manner be attributed to an excess of water. Still 
Case No. 9 was one of the most severe ones that I have yet seen, 
though it is underlaid by a stratum of gravel at a depth of from 
five and one-half to eight feet. The same is true, in different 
measures, of Cases 10, 11 and 12. The soil in Case No. 10 is de¬ 
cidedly sandy with a stratum of coarse granitic gravel at a depth of 
only three feet and yet this land is in such bad condition that the 
owner has not yet, after repeated attempts, succeeded in getting his 
fruit trees, peaches and pears, to grow. In Case 12 a beautiful 
orchard has been destroyed outright in one season. This point is 
not a matter of opinion but one of fact, and for this reason so 
many cases, to which Cases Nos. 16 and 20 might be added, have 
been given. The conclusion is evident that the trouble is not due 
to the presence of an excess of water, nor to the character of the 
soil for these sandy soils have shown it to as great a degree as 
heavier clayey soils of which Cases Nos. 6 and 12 may be cited 
as examples. No. 6 is an especially bad case, but the results were 
no worse than in Case 9—they could not be, for two and one-half 
acres of large trees were killed within a few weeks. The attack 
in Case No. 6 was not so violent nor did it involve so much ground 
at one time. 
The trouble is not to be attributed to ordinary alkali. In 
Case No. 8 a part of the orchard is free from the nitre but is 
rich in ordinary alkali; the trees have died only in the nitre area. 
There are many orchards scattered throughout the fruit growing 
