96 DISEASES OF GLASSHOUSE PLANTS 
(4) The fungus may carry on a saprophytic existence 
in rotten wood in the house and in paper used for blocking 
holes, and these constitute important sources of infection. 
(5) Straw manure removed from beds in infected 
houses was found invariably to harbour the parasite, and 
when allowed to remain unburnt in a heap outside the 
houses is a centre for the spread of the fungus. 
(6) The examination of “ flats’ was unsuccessful in 
obtaining positive evidence of their transmission of this 
fungus, but observations upon the incidence of this 
disease in commercial nurseries indicate the probability 
that it may frequently be carried in this way. 
(7) Manure fresh from country farms has proved to 
be free from infection with this organism. 
(8) Heaps of manure placed adjacent to those of decay- 
ing cucumber remains have been found to be infected. 
(9) Manure direct from town stables has in some cases 
been found to be infected. 
Other important sources of infection are the water 
supply and the clothes of workers in the infected nurseries, 
the latter having been found to be a most important 
method of disease transmission in the Lea Valley. 
As in the case of the Cercospora disease, humidity of 
the atmosphere has proved to be an important factor in 
the progress of the disease, which is considerably more 
rapid at humidities about 90 per cent than at those below 
60 per cent. 
During the fallow season the fungus is known to 
hibernate in various parts of the houses. This being so, 
the efficient cleansing of the houses forms an important 
part of the control of the disease. Fumigation by burn- 
ing sulphur has not proved efficient in this respect, and 
it is necessary to wash down the structure with oe 
cresylic acid, as explained in Chapter IX. 
Of the many spray fluids tested, those of liver of 
sulphur or lime sulphur have yielded the most promising 
results. One essential quality of first-class fruit is the 
presence of a perfect ‘“‘ bloom” on the surface, and in 
