82 
J. ROSENBAUM AND CHARLES E. SANDO 
predicting whether a certain tomato can or cannot be infected with Macro- 
sporium. 
Summary. 
In the development of a tomato fruit, the cuticular layer increases in 
thickness with the age of the fruit. Measurements to determine the resist- 
ance of the skin of tomatoes have shown that there is a definite and direct 
correlation between age and the resistance of the skin to puncture. 
Infection experiments with Macrosporium tomato on tomato fruit have 
shown that the amount of infection which it is possible to obtain decreases 
with the age of the fruit. 
While the results do not prove absolutely that the inhibition of infection 
is a purely mechanical one, the resistance of the tomato skin to puncture 
may explain, at least partially, the ease with which infection without previ- 
ous injury is obtained on the young fruit but not on the older fruit. 
Bureau of Plant Industry, 
U. S. Dept. of Agriculture, 
Washington, D. C. 
