MECHANIC DEVELOPMENT OF PATHOLOGIC TISSUES 409 



course, but should be able also to diagnose the more common diseases 

 and suggest remedies in the form of insecticides, or fungicides, or other 

 remedial measures from a knowledge of the physiology of pathologic 

 plants. A change in the soil, or a change in the temperature and 

 exposure may be all that is needed to keep a plant in a perfect state 

 of health. 



The problems which may be assigned to the post-graduate student 

 for experimental investigation are unlimited in America, where the 

 nation is confronted by serious pests introduced from various lands. 

 The anatomic and histologic characters and the development of cecidia 

 have been the subject of extensive studies in Europe, but American 

 botanists have done very little in the study of American galls along these 

 lines of investigation. The character of the poisons which cause 

 the stimulation of the plant to produce the galls is a matter well worth 

 the attention of botanists experimentally inclined. The equipment of 

 the laboratory and the facilities for experimentation should be con- 

 sidered before the problem is assigned to the post-graduate student. 

 The previous training and bias of the individual should be weighed 

 carefully for the research work may be of a cytologic nature. It may be 

 a histologic study pure and simple with pathologic tissues, or the prob- 

 lem may deal with prophylaxis, or preventive measures. It may be 

 that the student is better prepared to investigate the etiology of disease, 

 or the composition of sprays and their effects on the plant tissues. 

 Some advanced students would find keener zest in the systematic or 

 biologic study of some fungus, or group of fungi, or the bias may be 

 toward detailed experimentation with insects, or other forms of animal 

 life. The teacher should weigh carefully all of these details and act 

 accordingly. Problems with an economic bearing would be more suit- 

 able for the students of agricultural colleges and experiment stations, 

 while matters of pure science might be properly relegated to the 

 endowed colleges and universities, where investigation with a practical 

 trend would not be absolutely essential. The laboratory work should 

 be combined with field work in the study of inorganic and organic dis- 

 eases. The character of the field work will be determined by the 

 nature of the investigation and by the season and by the climatic con- 

 ditions. The work in the field at first would consist in the observation 

 of diseases, the taking of notes from the living trees and the collection of 

 material for more detailed study. The extent of the injury should be 



