DISEASED CONDITION OF PLANTS 47 
nitrogen the number of striped plants was considerably 
less. Further experiments were arranged in which 
inoculated tomato plants were given increasing amounts 
of potash and nitrogen. The progress of the disease was 
estimated by measuring the distance up the stem from 
the point of inoculation that the “stripe” lesions had 
travelled in a given time. The results showed that the 
lesions had travelled furthest where the largest amounts 
of nitrogen were given, and as the nitrogen was gradually 
reduced the height of the lesions became consistently 
shorter. As the amount of potash was increased the 
progress of the disease was reduced. Later experiments 
on commercial nurseries confirmed these results, and it 
is now common practice to induce tomato plants to grow 
away from “ stripe”’ by suitable additions of potash. 
An excess of nitrogen in the soil has long been known 
to increase susceptibility to some diseases, and in this 
respect the most easily assimilated forms, such as 
nitrates, have the most marked effects. On the cele- 
brated Broadbalk wheat plots at Rothamsted, those 
receiving an excess of nitrogen show a high susceptibility 
to rusts and Hpichle typhina, while the plots receiving 
the normal balanced fertilizer mixture are free from 
these diseases, although equally exposed to infection. 
Similar results were observed in respect of mangold leaf 
spot caused by Phoma bete. 
The manurial trials with wheat and barley at Woburn 
also indicated that the high nitrogen plots, especially 
those receiving sodium nitrate, are more susceptible 
to mildews than the normal plots. At Cheshunt the 
tomato experiments have long indicated similar results 
with regard to the incidence of some diseases. Thus 
the plots receiving heavy dressings of straw manure 
have consistently shown a greater number of casualties 
from root diseases than the other plots. Observations 
in the tomato and cucumber industry in the Lea Valley 
have provided abundant proof that methods of cultiva- 
tion favouring heavy feeding with nitrogenous manure 
