288 
Journal of Agricultural Research 
Vol. XXXI, No. 3 
diseased plant tissues whereby nitrates are converted into nitrite 
and ammonia. This result led this worker to attribute the disease 
in question and other diseases of similar nature to denitrifying 
bacteria. 
We are indebted to True and his associates (23) for extensive and 
thorough-going analyses of plants in disease and health made in 
connection with their studies on spinach mosaic. In this investi¬ 
gation ash content, oxidase reactions, carbohydrate production, and 
nitrogen metabolism of healthy and blighted spinach were compared. 
The last named phase of the work was carried out by Jodidi, Kellogg, 
and True (23, p. 385-404 ), and since this part of the investigation 
was most extensive and the methods employed have since been the 
basis of other investigations, it will be considered in some detail. 
They found, as a result of their comparative analyses, that in diseased 
spinach there was a lower percentage of total nitrogen and of acid- 
amide nitrogen than in healthy spinach, and they explained this 
relation by the assumption that denitrification takes place in those 
tissues whereby a part of the nitrogen is lost either as elementary 
nitrogen or in the form of ammonia. They also found a highe? 
proportion of ammoniacal nitrogen in the diseased material than in 
the corresponding healthy tissues, and the suggestion was made that 
the reason for this is also to be sought in the processes of denitrifi¬ 
cation, whereby a part of the nitrites is further reduced to ammonia. 
In 1920, Jodidi, Moulton, and Markley (13) reported additional 
analyses along the same lines as those of the previous year, in order 
to corroborate the early results by observations on spinach taken 
from various fields and at other seasons. The results of this work 
seem to agree closely with the results of the earlier work. The pres¬ 
ence of nitrites in the diseased plants postulated in the former article 
was definitely shown. 
Jodidi (12) in 1920 gave the results of analyses of healthy and dis¬ 
eased cabbage. The diseased cabbage analyzed by him is described 
as showing a metallic color between the veins, only the spaces nearest 
to the veins being green. The leaves were brittle and their margins 
were frequently of a uniform yellow color. Coupled with these signs 
there was a poorly developed root system and a stunting. It is 
definitely stated that preliminary experiments to demonstrate the 
infectious nature of the disease had thus far led to negative results. 
The work previously mentioned had shown a certain type of the 
nitrogen distribution in mosaic spinach as contrasted with that in 
healthy spinach. Jodidi found that the diseased cabbage showed 
the same relations in the chemical constituents as compared with 
the healthy cabbage, and he concluded: “Judging from the strik¬ 
ing similarity of the analytical evidence presented with regard to the 
various nitrogenous compounds occurring in healthy and blighted 
spinach plants, on the one hand, and in normal and diseased cabbage 
plants on the other, and taking into consideration that spinach 
blight belongs to the type of mosaic diseases, it appears logical to 
relate the cabbage disease caused by denitrification to the latter type.” 
Further contributions to the biochemistry of plants in health and 
disease have been made by Willaman and Sandstrom (28), but in 
this work the chief emphasis has been placed upon other constituents 
than the nitrogenous ones. 
