200 BOTANICAL GAZETTE [FEBRUARY 
of sugar beets, curly dou of potatoes, mottled leaf of potatoes, and mosaic 
disease of tobacco. Nitrites and ammonia were detected in the juices ex- 
tracted from diseased plants. Their origin is supposed to be due to the 
action of nitrate-reducing bacteria, since the presence of these bacteria in the 
tissues runs parallel to the presence of nitrites and ammonia. The idea is 
advanced that the characteristic symptoms in all of these diseases are due to 
nitrogen starvation. The plants are deprived of nitrates taken up by the roots, 
because of their bacterial reduction to nitrites and ammonia. 
The increase of the oxidases in the tissues of plants affected with some of 
these diseases has been well established. This biochemical phenomenon is 
easily incorporated into the author’s hypothetical scheme. The results of 
an exhaustive microchemical study, including a histological method for the 
detection of oxidases, are said to indicate that the increase of the oxidases in 
the plants affected with bacterial nitrogen starvation is a direct effort of the 
physiological functions of the plants to overcome the reducing forces of the 
bacteria. In making such a statement it must be assumed that the oxidation 
of phenol derivatives by plant tissues is a measure of their power to oppose 
nitrate reduction. Experiments are recorded and arguments brought forth 
to show the increased tendency and effort of the diseased plant to make good 
the loss of nitrates by bacterial reduction. These arguments are not easily 
followed, as they seem to be based upon the theory that the absorption of salts 
by plants is a function of the amount of water taken up by the roots. 
The announcement of the apparent ease with which supposed causal 
organisms have been isolated from tissues of plants affected with this class of 
disease is rather startling, since several years of persistent effort by a number of 
workers has hitherto failed to establish definitely the parasitic character of 
these diseases.—Cuas. O. APPLEMAN. 
