6 TRANSACTIONS OF THE [Sess. lxxvi. 



air-content, etc. Then we have the atmospheric conditions, 

 namely, temperature, moisture, precipitations, lighting, wind, 

 etc., the conditions of soil and atmosphere ; in other words, 

 the climate varies with latitude, altitude, aspect, and ex- 

 posure. Man has but little power to ameliorate the atmo- 

 spheric conditions, but he often does the opposite by allowing 

 air to become polluted b}^ smoke and poisonous fumes, thus 

 producing conditions highly inimical to plant life. 1 On the 

 other hand, something may be done to ameliorate the soil 

 conditions. For example, by draining, manuring, and 

 cultivating. As regards altitude, exposure, and aspect, 

 man can select and cultivate species or varieties in those 

 localities or situations where each is likely to find its nearest 

 approach to its optimum conditions. 



The organic environment is supplied by the plant and 

 animal kingdoms. In the vegetable kingdom we have 

 plants in competition with, one another for the best soil 

 and air space. We have also the saprophytic and parasitic 

 forms. The soil bacteria are not the least important 

 members of the organic environment, although mentioned 

 last. 



The science of Mycology is of the greatest importance in 

 pure and applied botany. Fungi play a very important 

 role in nature as saprophytes and parasites. Many forms 

 have by careful selection and cultivation been pressed into 

 the service of man in such important industries as cheese- 

 making, bread-baking, wine and cider preparation, brewing, 

 distilling, etc. 



The cultivated mushroom and the numerous wild edible 

 forms, only too little known, have their importance as food 

 plants. Finally, the study of the parasitic disease-causing 

 forms is of the highest theoretical and economic importance. 



Pure science in investigating the effect of disease aims at 

 discovering the changes of the living substance and tissues. 

 It may be called Cytopathology. Applied science considers 

 the influence of disease on the plant as regards its economic 

 value. We must combine both in order to understand the 

 phenomenon from an economic standpoint. 



1 The question of smoke and fume damage to plants is receiving 

 greater attention than ever on the Continent. Such damage has 

 increased enormously with increasing industrial development. 



