

298 BOTANICAL GAZETTE [april 



is well known; also the taking over of the lime-sulphur mixture 

 from the entomologist. The susceptibility of certain varieties of 



farmer 



some 



berries. The florist, likewise, has been obliged to eliminate certain 

 varieties of carnation. They would have done so had no science 



ogy existed. Similarly, many 



farmer 



highly resistant or are of such poor quality that they are not used 



extensively. 



pessimistic 



of science to plant pathology, I shall say at once that though these 



£3 



made in the main empiric 

 >d and made easier bv the f 



fostered by basic knowledge in mycology, bacteriology, and 



physiology; and definitely aided by a 

 special technique. With the remaining 



ances 



upon science is direct and evident. For example, knowledge of the 

 alternate host relation in pomaceous rust and currant rust could 

 not have been attained without the upbuilding of a broad knowledge 

 of the rusts in general, indeed of the fungi as a whole; nor could 

 the canker relation in apples (Glomerella, Sphaeropsis, Bacillus) 

 have been found without knowledge of the nature and morphology 

 of the causal fungi ; and the same is true of the present troublesome 



citrus canker. Adeouate Quarantine insnert.inn 



measures 



without definite knowleds 



causes of disease. 



looms 



mi 



interstate and international. The following are examples of 



mi 



pear blight, asparagus rust, grape anthracnose, cabbage club root, 

 potato wart, potato blight, grape blackrot and downy mildew, 

 chestnut bark disease. 



Seed transference of disease is exemplified in the cabbage 



and 



It 



is barely possible, but not at all probable, that this relation could 

 have been discovered without intimate knowledge of the causal 



