DISEASES DUE TO FUNGI 57 
were removed as they became infected to eliminate the 
factor of spread. The remainder were untouched and 
indicated the rate of superficial spread of the fungus (5). 
TABLE lI. 
No. of Seeds Average per cent Diseased Seed- Average per cent Diseased 
per Box. lings Removed when Attacked. Seedlings not Removed. 
600 51 100 
300 45 100 
200 49 100 
100 42 78 
50 37 46 
25 35 41 
The second column, Table 1, shows the uniform 
results obtained when the seedlings were removed as 
they were attacked, and indicate that the number of 
seedlings primarily attacked depends upon the number 
of disease centres in the soil and not upon the closeness 
of sowing when the factor of superficial spread of the 
organism is eliminated. In the third column, where the 
fungi were allowed to remain, the spread of the organism 
is more rapid where the seeds are sown closely than 
where they are sown thinly. In the closer sowings the 
density of the plants increases the film of water adhering 
to the seedlings and offers a ready means of spreading 
the disease through the box. Sowing above fifty to the 
box should be avoided, for this materially assists the 
disease. A film of water over the surface of the soil is 
necessary for the rapid spread of the disease, and water- 
logged conditions are also in its favour. Moistening the 
soil through capillary attraction by standing the boxes 
in shallow trays of water is less favourable to the disease 
than watering from the top. Temperature is important, 
and relatively low temperatures—about 10° C.—are less 
favourable to the disease than high temperatures of 
23° C.-27° C. Thus summer sowings of tomato seeds are 
more liable to “ damp off”’ than early spring sowings— 
