194 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



chlorotic condition might result from an extensive development 

 of oxidizing enzymes. Unfortunately, this would not explain the 

 condition prevailing where the tissues are hyperplastic, though, 

 if found consistent, it might explain the hypoplastic relation. 

 Moreover, the suggestion that oxidase inhibition upon diastase 

 would explain tho accumulation of starch in diseased tissues 

 does not well apply, since the si arch accumulation has been shown 

 by Freiberg ('17) and Dickson ('22) to be in the greener areas, 

 a finding confirmed by ourselves. Finally, Allard ('16) has 

 convincingly demonstrated that the infective agency and oxidase 

 are not the same, for a differential and quantitative destruction 

 of the oxidase does not affect infectivity, whereas it is possible 

 also to destroy the active agency in the mosaic disease and yet 

 demonstrate oxidase action. Woods ' viewpoint has been adopted 

 also by rleintzel ('00), and in part by Chapman ('13). After 

 criticising (Hunger, '03) the oxidase theory of Woods, Hunger 

 ('05) regards the disease as a nutritional one possessing the 

 peculiar property of being "physiologically autocatalytic, " acting 

 by contact and also able to regenerate itself. In some work done 

 in this laboratory Freiberg ('17) also advocated the enzyme 

 viewpoint rather than the more general virus effect, but he con- 

 sidered the enzyme to possess none of the nature of oxidases. 

 The idea that it may be an enzyme was based in part on its ab- 

 sorption by talc, on the specificity of the reaction between 

 the mosaic agency and formaldehyde, and likewise on the basis of 

 the resistance of the body to antiseptics in general. Just how the 

 reproduction of such an enzyme might be accomplished was not 

 considered in detail, but was accounted for on general physiologi- 

 cal grounds. In this connection attention was drawn to the fact 

 that upon the injection of the toxin of Bacillus diphtheriae into a 

 healthy patient, the usual pathological condition results, that is, 

 the production of lesions characteristic of that disease, apparently 

 with the production of additional toxin in the system. 



THE BACTERIAL THEORY 



In one of the earliest of the scientific reports on the mosaic 

 disease of tobacco, that of Mayer ('86), bacteria were regarded 

 as the causal agency, although no satisfactory proof was afforded . 



