1921-22.] BOTANICAL SOCIETY OF EDINBURGH 83 



huge literature has been created on the diseases of rubber, 

 tea, coffee, sugar-cane, cotton, etc. 



The treatment of plant diseases may be described as a 

 collection of scraps of experience, up till the early part of 

 the nineteenth century. Sulphur as a fungicide for peacli 

 mildew was known in 1821, and the combination of lime 

 and sulphur used in 1851 was the beginning of the lime- 

 sulphur fungicide so much in use now. The use of copper 

 sulphate against fungi may have been known earlier, but 

 it was Millardet of Bordeaux who, about 1885, realised the 

 merits of a combination of copper and lime in the well- 

 known "Bordeaux mixture." Formalin does not appear 

 in books as a fungicide till after 1896. 



Our knowledge of plant hygiene or how to keep plants 

 healthy is still mainly empirical. A promising beginning 

 has been made with " immune varieties." The results 

 obtained in France, about 1890, through using vines of 

 American origin, by grafting or by hybridisation, attracted 

 attention. Eriksson in Sweden, MacAlpine and others in 

 Australia, and Bifien at Cambridge have attained good 

 results with varieties of wheat immune to rust. In more 

 recent times the success of varieties of potatoes immune 

 to wart disease has saved this country millions sterling. 

 The discovery of immune varieties is an important branch 

 of plant breeding which, combined with modern methods 

 of mycology, render it probable that the future will combat 

 plant disease by preventing it. 



This brief survey may suffice to emphasise that the 

 progress of applied botany depends on the utilisation of 

 the latest -researches of botany as a whole. Conversely, 

 that the stimulus to further investigation in botany may 

 come from the problems incidental to agriculture, forestry, 

 and horticulture. Taxonomy or systematic botany has 

 raised men skilled in detecting the differences in varieties 

 so essential in plant breeding. Plant physiology with its 

 laboratory equipment has placed the understanding of 

 plant nutrition and plant response on a firm basis. Ecology, 

 in its endeavours to ascertain the relation of plant to soil 

 and climate by a study of the native plants, has led to a 

 better concept of the utilisation of land for economic 

 purposes. Mycology is saving millions sterling of crops 



