DISEASES OF CULTIVATED PLANTS 331 
While these methods and rules are stated with special reference 
to bacteria as the cause of disease, they apply with equal force to 
the proof of cause in the case of any given parasitic fungus. These 
methods require rigorous and exact work in the isolation and subse- 
quent culture of the parasite upon sterile media, followed by equally 
careful inoculation work using these pure cultures as a source of the 
organism. 
METHOD OF INOCULATION FROM CULTURES 
The methods of inoculation tried by the investigator are of great 
importance. ‘These determine, in fact, the success or non-success 
of his efforts. There must be adaptation of the method to the life 
history of the parasite and the developmental stages of the host 
plant, including the appearance of the parts more commonly attacked 
by it. 
Fig. 13. This shows method of infecting field plots by means of the hand spray pump, using the 
washings of samples of wheat and other grains. The washing of grain containing spores of disease 
such as anthracnose or scab may be used, Cultures may also be sprayed upon plants in this way or 
by means of blow-bottle in smallertests. (From Bul. 203, Ohio Experiment Station). 
Following the methods of earlier bacteriologists, needle pricks 
are often employed both in the inoculation of fungi and bacteria into 
plants. One seeking to pursue a special line of inoculations will need 
in all cases to study his conditions as wellas the methods of other 
investigators. ‘Thus, doubtless, inoculations like those of Phytoph- 
thora and Plasmopara may be best attained by using drops of sterile 
water to carry the spores. The same principle applies in field 
