igoj] Journal of the Mitcheu, Society. 73 



of a disease, however thoroughly it may seem to have been 

 studied before, may lead to important development is well 

 illustrated in the case of the familiar pear blight, which, 

 though known for ages and the topic of masterly classic 

 research, has recently, under trained observation and critical 

 interpretation and experimentation, revealed new secrets 

 leading to more masterful and complete control. The large 

 fields of plant pathology, grouped under the term 'physiologi- 

 cal disorders,' are still practically unworked; diseases due to 

 false nutrition, absorption or assimilation, or to impaired car- 

 bon assimilation owing to improper environment, to crowding 

 or shading or to hereditary inabilities. A start has been 

 made sufficient to show the importance of the results await- 

 ing. 



The recent discovery of the ultramicroscopic organisms or 

 filterable enzymes which has robbed the bacteria of the dis- 

 tinctioin of being the smallest of living things opens a new 

 field in both plant and animal patholog} T comparable in kind, 

 though probably not in magnitude, with the creation of bac- 

 teriology by Pasteur. It is yet unknown whether we have to 

 do here with organisms or enzymes, and contemplation of the 

 problems awaiting in this realm places us in a position to 

 appreciate more fully than ever before the great controversy of 

 spontaneous generation as fought in the sixties. The 

 announcement in a recent periodical of the discovery of solu- 

 ble protoplasm emphasizes the existence of a vast unknown 

 covered by the words protoplasm, enzymes, invisible organ- 

 isms. Is it coincidence of fate that with the growing impor- 

 tance of the problem of the invisible organism there comes 

 the invention of a microscope of surpassing excellence with 

 which the seeing of molecules is a hoped for possibility? 



The science of plant pathology is indeed young. It has 

 yielded much, and it is still full of promise. In the achieve- 

 ment of the results to come draught will be made upon the 

 sister sciences even more than in the past. Plant physiology 



