Interrelation of Plant and Animal Pathology 65 



occurs in many human diseases. In this connection, some interest- 

 ing results were secured last year by Mr. Haenseler, a graduate 

 student in my laboratory. Convinced that a study of unicellular 

 algae in their relation to fungus parasites should simplify the prob- 

 lem experimentally, I set him to work on Spirogyra and its para- 

 sites. His results were remarkable in that they indicated at least 

 a suspicion of attempted phagocytosis in a unicellular alga, though 

 it may prove to be an effort on the part of the spirogyra cell to 

 thicken its wall against the invader, as Brullova found in the case 

 of Vaucheria. 



It is very significant that pathogenic organisms both fungi and 

 bacteria lose greatly in virulence, for either animal or plant host, 

 on being cultivated in artificial media. 



It is very probable that if plant pathology is ever to repay its 

 debt to animal pathology as the pioneer in the discovery of the 

 essential principles of acquired immunity to disease, it will be in 

 the direction of the cause of cell resistance. This is unquestionably 

 the chief problem in hereditary resistance. The facility with which 

 unicellular plants can be manipulated and observed experimentally 

 should enable the subject to be approached from this direction with 

 at least som.e probability of definite results. 



All these facts brought out by the careful researches of modern 

 biology serve to explain more and more thoroughly the details of 

 the intense struggle for existence, in which every individual from the 

 highest animal to the lowest plant must take part. Every individual 

 is supplied with weapons of defence or of offence, some great and 

 some small, and in this grim competition the race is not always to 

 the swift or the battle to the strong. 



