hosts, of the fungi that are attached to the roots of many 

 of our common forest trees? To what extent is the fer- 

 tility of the soil dependent upon the microscopic or- 

 ganisms that occur in it, the bacteria, the fungi and 

 oilier organisms? Is the pollution of the atmosphere of 

 our cities inimical to the continued growth and life of 

 trees? Are the gases of automobile exhausts detrimental 

 to vegetation ? To what extent can growth be accelerated 

 by skilful hybridization and thus the production of trees 

 economically important be quickened? To what extent 

 can production of the sugars and starches in plants, the 

 ultimate source of all food supplies, be controlled by 

 standardizing the conditions of temperature, moisture 

 and the composition of the atmosphere under which the 

 plants are grown? The diseases of plants are an untold 

 source of pecuniary loss to man. They offer many 

 analogies to the diseases of human beings, but it seems 

 probable that in the future the most economic way of 

 dealing with them will be, not by waiting until the dis- 

 ease has appeared and then endeavoring to cure it, but 

 by producing races of plants that possess inherited im- 

 munity to disease. There are, moreover, many funda- 

 mental problems of disease-processes in living beings 

 that can probably be studied more readily in plants than 

 in animals or man. For all these problems here men- 

 tioned and hosts of others that might be mentioned, the 

 Garden possesses unusual facilities in its site and its large 

 collections for the best and most fruitful types of in- 

 vestigation. They are problems that require the use of 

 the experimental method, the method which more than 

 any other has been instrumental in the phenomenal ad- 

 vance of science that has characterized recent years. 

 Many of these problems require long-continued experi- 

 mentation and thus can be attacked far better in an 

 endowed institution such as the Garden, than in a state- 



[ii] 



