1908.] PUBLIC DOCUMENT — No. 33. 141 



was cut back to a ])oint about 2 centimeters above the first 

 leaves. In from one to two weeks all the pruned plants 

 showed symptoms of the disease on the new growth, and con- 

 tinued to show it tliroughout the growing season. None of the 

 unpruned })kints showed the slightest indication of the mosaic 

 trouble at any period of growth. 



There appeared to be no difference in the intensity of the 

 disease in anjf^ of the boxes, and when the diseased plants in 

 the boxes were compared with plants of the same age grown 

 in soil and pruned back at the same time, no difference in in- 

 tensity of the disease could be noticed, so it would appear from 

 this experiment that excess of plant food will not produce or 

 intensify the mosaic disease of the tomato, although it has been 

 observed that an excess of nitrogenous fertilizers does intensify 

 the disease in tobacco, as well as that an excess of lime tends 

 to lessen it,^ and there are characteristics displayed by plants 

 resultino; from overfeeding- which resemble the mosaic trouble. 

 In our experiments with the disease on tobacco these views 

 have been borne out, and it has also been noted that the to- 

 bacco is far more susceptible to those changes which bring 

 about the disease than is the tomato. 



Calalase in Tomato Leaves. 



Some leaves of a perfectly normal tomato plant were treated 

 to ascertain the presence or absence of the enzyme catalase, 

 which has been so well described by Loew,^ as it occurs in 

 tobacco. As only green tomato leaves were available, they 

 were taken and ground up in a mortar with fine quartz sand and 

 a little water. After the leaves were in this manner thoroughly 

 disintegrated the mass was covered with a .2 per cent, solution 

 of ammonium carbonate (NH^)2C03, and set aside for three 

 hours in a room the temperature of which was 25° C. After 

 standing for this length of time the mixture was filtered 

 through a coarse filter, and the resultant mixture filtered again 

 through a finer filter paper. 



The residue, consisting of pulp and quartz sand, was allowed 



1 Mosaic Disease of Tobacco. A. F. Woods, Bulletin Xo. 18, Bureau of Plant Industry, 

 United States Department of Agriculture. 



2 Catalase. Oscar Loew, Report No. 68, Department of Vegetable Pathology and 

 Physiology. 



