106 THE PLANT WOKLD. 



to characterize one of our well-known text-books as a "Text-book 

 of Plant Diseases Induced by Cryptogamic Parasites/' when it 

 is little more than a catalogue of cryptogamic parasites which 

 cause disease ! Such important features as symptoms, patholog- 

 ical anatomy, prognosis and extent of injury, and treatment and 

 prophylaxis, often receive only bare mention or are passed over 

 completely. The importance of careful and accurate observa- 

 tion in the field in regard to the symptoms attending the pro- 

 gress of the various diseases cannot be overestimated. Many 

 of the facts which must be incoi'porated in our future pathol- 

 ogies cannot he obtained from the dry herbarium specimens of 

 the best pathological or mycological collectors, but must be re- 

 corded in the field while the patients are still alive, and not 

 after they are dead and stored away in herbarium sepulchers. 



In field work in plant pathology it is also highly desirable 

 to make detailed and accurate obsers^ations and records in regard 

 to the various factors which might favor or retard the develop- 

 ment of the disease, such as amoimt of clear and cloudy weather, 

 amount of rainfall, character of soil, soil treatment, amount -of 

 soil moisture, and other climatic or edaphic factors. Also the 

 condition of the host plant itself should not be overlooked, at- 

 tention being paid to evidences of deviation from the normal 

 physiological tone due to other factors than the disease under 

 consideration, as by this mean:^ much in regard to what may be 

 teraied predisposing causes may be learned. 



By accurate and painstaking field work, the determination 

 of the extent of injury from the various diseases must be re- 

 moved from the realm of mere guesswork. Too often our esti- 

 mates of the amount of damage from a given disease are based 

 on superficial examination and are consequently far from accu- 

 rate. The injurv is o^enerallv overestimated, but occasionallv 

 the figures fall below the true amount. The camera is a neces- 

 sary and useful article in field work, but while photographs 

 often show graphically the extent of injury, quantitative meth- 

 ods must be adopted in this line of field work whenever possible. 



The value of quantitative methods may be noted, for ex- 



