Von SCHRENK: TEACHING OF VEGETABLE PaTHoLocy 65 
cannot be rigidly maintained, nor is it desirable. The various fac- 
tors work too closely one with or against the other, but with care, 
each can be emphasized at the proper time. The theoretical con- 
siderations of immunity, the symptoms of disease, the spreading 
and the nature of disease, must go hand-in-hand with the experi- 
mental work, but should at all times be subordinated to it. Ques- 
tions such as that belong to the end of a course, after the student 
has thoroughly grasped the meaning of the complex interrelation 
of plants to each other and their surroundings. Personal ac- 
quaintance with one or more diseases, and a careful analysis of 
each, will lead to a broader conception of disease by itself, and 
will make a more lasting impression on the student when he must 
puzzle over these questions on his own account. Nowhere is too 
much teaching to be deplored more than in experimental work of 
the kind mentioned above. 
