No. L] FUNGOUS DISKASKS. 439 



of controlling thcni. Thr greater jKirt of our knowledge con- 

 eerning the control of greenhouse diseases has been derived 

 from the intelligence and skill of the progressive gardeners, 

 whereas, in the case of outdoor crops, the experiment stations 

 have been foremost in oti'ering suggestions for their control. 

 The trained agriculturist can consist(nitlv trive information in 

 regai'd to the control of specific diseases aftecting outdoor 

 crops with which he is more or less familiar ; but in cases of 

 greenhouse croi)s the methods of treatment arc so ditferent, 

 and require such an insight into the jilant re({uirements, that 

 it is almost necessary for one to be an expert grower, or at 

 any rate to understand something about the normal conditions 

 of the cro}), before his judgment or advice is worth much. It 

 is necessary, at least, that he should })()ssess a thorough 

 understanding of the influence on plants of the three cardinal 

 factors, heat, light and moisture, and the role they play in 

 the production of normal cro})s, together Avith their relation- 

 ship to the development of disease-producing organisms. 

 Such matters as soil texture and soil fertility also constitute 

 imi)ortant features which are necessary to understand. The 

 gi-eat attention necessary to give to such matters as heat, 

 moisture and light in greenhouse culture is only appreciated 

 by the trained gardener. Some of the most troublesome and 

 disastrous diseases are entirely controlled by the intelligent 

 use of these factors, and others, which are more or less com- 

 mon, could no doubt be controlled or greatly alleviated if 

 modifications in the method of growing certain crops were 

 practicable. 



The benefits which have resulted from spraying out-of-door 

 crops have unfortunately been the means of inducing some to 

 believe that spraying is the only method of treating plant 

 diseases, and where spraying is not recommended as a remedy 

 their enthusiasm diminishes. We have gi*own for some 

 years many experimental crops in the greenhouse, and we 

 have seldom had occasion to see the need, or })ossible benefit, 

 to be derived from spraying. In the elimination of diseases 

 from greenhouse crops the ultimate aim should be to select 

 varieties of plants which are immune to disease, as well as 

 to study and devise conditions which will not favor the 



