158 "Damping off'' etc., of Tomato Seedlings 



and seeds remain in this state varies considerably, but experiment 

 shows that three or four days are sufficient to destroy the mucilage and 

 allow of its easy removal. It is unnecessary and undesirable to allow too 

 long a time for this preliminary rotting of the mucilage. After the 

 fermentation the seed is washed and dried. To reduce the possibility of 

 infection the extraction should be carried out under hygienic conditions, 

 and away from the vicinity of the growing plant where there is danger 

 of contamination from fungus spores in the air. The fruit should be wiped 

 with a rag containing a little lysol or cresylic acid or sprayed with a 

 2 per cent, solution of formaldehyde in order to sterilise the outside. It 

 must then be well washed, dried and carried to some clean shed or room, 

 where the air is still, and there the seed should be removed. 



An examination of many different samples of seed has shown that 

 they carry on their testas a very varied fungus flora, but so far we have 

 been unable to find any active parasites. This, of course, does not prove 

 that tomato seeds never carry destructive organisms but it indicates 

 that such is a rare occurrence. The hairiness of the seed coat and the 

 presence of many fungus spores point to the fact that disease organisms 

 may be carried also. In this connection it is interesting to note that 

 I. Massee 1 has described the presence of hibernating mycelium of 

 Macrosporium solani underneath the seed coat in samples of tomato 

 seeds she examined. It is advisable to test all bought seed in a trial 

 box under sterile conditions some time before the general sowing. Seed 

 suspected of impurity should be sterilised. Home produced seed should 

 be free from disease, provided it is derived from the best fruits and has 

 been extracted under hygienic conditions. 



Seed-boxes and Pots. 



General observation and experimental work show that the disease 

 organisms are carried over from one season to the next by seed-boxes 

 and pots. Discolouration and destruction of plant roots has frequently 

 been traced to some crack or crevice in the pot or box which has har- 

 boured the resting spores of the fungus. 



The Soil. 



The organisms producing "damping off," like many others, spend 

 part of their existence in the living plant and the rest in hibernation 

 over the winter in the decomposing soil humus. So far as we have been 

 able to determine, "damping off" of tomato seedlings is produced by 



1 Massee, I. Kew Bulletin, No. 4, 1914. 



