Journal of Agricultural Research 
Vol. XXI, No. 3 
162 
about 3 months old. The results with the young western yellow pine 
(fig. 2) are more striking than those with the older stock. Autumn 
losses, presumably due to late damping-off, were not affected by the 
treatments; but winterkilling was entirely prevented (Table I). The 
heaviest treatment seemed to give better results than the lighter ones, 
so far as correcting chlorosis was concerned, both at the fall and the 
succeeding spring examinations, but resulted after the third treatment 
in the blackening of some of the leaves. The chemical injury was even 
more marked at the time of the spring examination, when practically 
every seedling in all the western yellow pine plots treated with the 2 per 
cent solution showed chemical injury, whereas the plots treated with 
the weaker solution showed none. 
With young Douglas fir (fig. 3) the amount of chlorosis initially present 
was less, and the untreated seedlings as well as the treated improved in 
color during the course of the experiment. In so far as chlorosis is 
corrected, the results are similar to those secured with western yellow 
&9TSS of exAM/mr/oN. 
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Fig. 3 —Graph showing the effect of a ferrous sulphate spray treatment on chlorosis in seedlings of Douglas 
fir a to 5 months old. 
pine. On Douglas fir, however, the heaviest treatment was no more 
effective against chlorosis than the lightest; the intermediate gave the 
best results. In view of this and the injury to western yellow pine from 
the strongest solution, it appears that only the intermediate strength 
(i per cent) should be used on conifers, at least if repeated spraying is 
practiced. 
Though the total area counted in all the spraying experiments with 
first-year seedlings was small—12 square feet in the treated plots and 
6 square feet in the controls—the data obtained from the counts show 
on the whole such consistent and decided improvement in the sprayed 
plots as to leave no reasonable doubt about the therapeutic value of the 
treatment for western yellow pine. Observations on the entire area of 
the western yellow pine experimental plots (200 square feet treated and 
120 square feet in the controls) indicate that the sample areas on which 
the counts were made were reasonably representative of the entire plots. 
