120 PLANT DISEASE 



is of great importance. So important do I 

 think this point that I believe it constitutes 

 the difference between immunity and non- 

 immunity to rust fungus. In other words, 

 if you have a field rich in all the essential min- 

 eral constituents, in an assimilable form, and a 

 green crop be grown in this field and ploughed 

 in, and then a cereal crop be grown, this 

 cereal crop will be immune to rust, to say no- 

 thing of other parasitical diseases. 



While if in another field, very deficient in 

 these assimilable mineral constituents, a green 

 crop was grown of a chlorotic nature, and 

 ploughed in, then the cereal crop grown would 

 not be immune owing to the imperfect chemical 

 functions performed by what I may call a 

 chlorotic humus. 



RUST IN WHEAT 



From the report of the Rust in Wheat Con- 

 ference held in Adelaide in 1892, 1 have come 

 to the conclusion that the debility lies in the 

 straw. My reasons for saying this are the 

 following 



In the first place, the straw of many crops 

 becomes laid although there is very little 



