DISEASES OF CULTIVATED PLANTS 309 
always of use in dealing with plant diseases. Ifthe soil is too wet, 
drain it; if late growth predisposes to winter injury, avoid such 
growth; if overbearing weakens plants, prevent, it by thinning 
the fruit. 
The philosophy of seed treatments is stated under diseases 
which infest the seed; that of soil treatments or disinfection, under 
soil infesting disease, and the general doctrines of sprays, fungi- 
cides, etc., under that heading further on. The progress made in 
plant disease prevention throughout the world during the period of 
about 26 years which has elapsed since the discovery of Bordeaux 
mixture in France shows how well adapted that discovery was to 
the needs of the times. 
The progress made in recent years in the study and control of 
plant diseases has been made possible by the agencies recently 
developed in the United States in the Agricultural Colleges, the 
Agricultural Experiment Stations and the United States Depart- 
ment of Agriculture. It is not expected that this advance in our 
knowledge of the diseases of plants or of the methods of disease 
control will soon wane. Efforts like the present one to present 
briefly the doctrines of disease and the philosophy of disease con- 
trol together with brief descriptions of prevailing diseases in our 
state, have for their purpose the wider dissemination of the body of 
present day knowledge int’ ¢ lines. Such a statement will not 
close the march of progr nor make less the need for more 
knowledge. Itis hopedt ‘cultivators of plants, whether farmers, 
gardeners, horticulturists or florists will find suggestive statements 
of information in the bulletin by which they can direct their own 
efforts to better advantage and correct or broaden their own in- 
ferences from observed conditions about them. All such results 
will not only increase the need for more knowledge, but will furnish 
impetus to the movements by which we will gain the desired 
information. 
In the preparation of the revised edition of the original Bulletin, 
No. 121, the general part immediately following this introduction 
has been considerably enlarged and brief discussions are now given 
concerning groups of plant diseases as well as those concerning 
parasitic fungi. It is fully apprehended that the host plant is the 
center of practical as wellas economic interest and these statements 
concerning enzymatic diseases as in the case of peach yellows and 
mosaic disease of tobacco, diseases transmitted in the seed, soil 
infesting diseases, and the relation of the spread of certain diseases 
to leaf biting insects are given as aids in mastering the principles 
involved. ‘The same aim has governed the discussions upon wounds 
