858 REPORT— 1897 



attention to the selection of those varieties of the cereal which are least predisposed 

 to rust. 



"When we find the annual losses from wheat- rust alone put down at sums vary- 

 ing from 1,000,000/. to 20,000,000/. in each of the great wheat-growing countries 

 of Europe, India, Australia, the United States, and elsewhere, it strikes one as very- 

 remarkable that so little should be done to encourage the scientific investigation 

 of these practical questions. I need hardly say that the establishment and main- 

 tenance of a fully equipped laboratory and experimental station does not cost the 

 interest on the smallest of these sums. 



It should be also clear that in the further development of our knowledge of the 

 treatment of parasitic diseases of plants the farmer, gardener, and forester can 

 alone supply the experimental evidence which will enable us to put theory to the 

 test in the field, garden, and forest. The botanist, by means of his pure cultures 

 of the fungus, can now show clearly what stage in the life-history of a parasite is 

 vulnerable. In his ' microscopic gardens ' he can show what antiseptics may be 

 employed, how strong they should be, and when and how they should be em- 

 ployed. 



But we must not forget that it is one thing to kill a fungus when grown pure, 

 and another to kill it when growing on or in, or even associated with, other plants, 

 without harming the latter. We may compare the first case to the destruction of 

 weeds on a gravel path, where the antiseptic dressing may be employed lavishly 

 and at any time, because there are no other plants to injure ; but it is another 

 matter to kill the same weeds growing in a lawn or a flower-bed, where we have 

 to pay attention to the neighbouring plants. 



Experiments in the open, simple in themselves, but conducted intelligently 

 and with due regard to the rigorous demands of science, can alone determine 

 these questions. 



Brewers have long known that burning sulphur in the barrels will rid these 

 barrels of the moulds and yeasts growing on their damp beer-soaked sides ; and 

 Berkeley saw clearly that sulphur could be applied to the outside of plants on 

 which such fungi as the hop- or grape-mildew, &c., are growing, the critical period 

 being when the spores are germinating, so that the slowly oxidising sulphur shovdd 

 evolve sulphurous acid in just sufiiicient quantities to destroy the delicate germs 

 without injuring the leaves. And even better results have been attained witb 

 Bordeaux mixture. 



But it is clear that this can only be done with an intelligent appreciation of 

 the life-history of the fungus, and a knowledge of when the germinating stage is 

 at hand. Tlie successes obtained in France and America with Bordeaux mixture 

 attest this. 



It would obviously be absurd to powder sulphur or spray liquids over 

 plants attacked by bunt- or smut-fungi, for we know that the germ-tubes only 

 infect the germinating grain as its first root emerges. Here, as was shown long 

 ago, and especially by the experiments of Hofimann, Kiihn, and De Bary, the 

 practice known as ' dressing the grain ' must be followed. Knowing that the 

 spores of the fungus are attached to the grain, or to particles of soil around, the 

 efforts must be directed to covering the outside of the grain with an antiseptic 

 which is strong enough to kill the germs but not the grain. If the land is known 

 to be clean, the grain may be immersed in hot water, the temperature being 

 experimentally determined, and high enough to kill the spores but not the wheat, 

 and so on. In these matters also the American stations have done good work. 



Neither of these classes of treatment can be adopted, on the other hand, for 

 diseases such as ' Finger and Toes,' where we have a delicate slime-fungus making 

 its way into the roots already in the soil ; but, here again, intelligently devised 

 experiments, such as those of Somerville and Massee, have shown that liming 

 the soil renders it so unfavourable to this disease that it can be coped witb. 



And similarly with other diseases ; the particular methods of dealing with the 

 'damping-ofi'' of seedlings, ' dry-rot ' in timber, the various diseases of trees, and 

 60 on, do and must differ in each case, and the guiding principle must be always 

 the same — having learnt all that can be learnt of the habits of the fungus and of 



