Synopsis The science of bacteriology, which has been so much " the domain of the student of disease, is now being applied to the elucidation and solution of many of the problems which confront the farmer, gardener, and dairy-man in their daily life. The extensive development of the dairying industry has been greatly assisted by the bacteriologist, and very material advances may be expected in the near future in the application of the science to the study of the soil and the phenomena connected with the economical and efficient use of fertilisers for the nutrition of farm and garden crops. For some time a knowledge of bacteriology has been  demanded of candidates for examinations in agriculture, dairying, and horticulture, but experience has  shown that few of them have had any practical acquaintance with the subject, mainly, we believe, from lack of suitable opportunities for proper training and absence of a text-book dealing with the subject in a practical way.

It is to supply the needs of such students that the present text book has been written. It is hoped also that it will be useful and interesting to agriculturists and horticulturists generally who are anxious to obtain an insight into the causes and methods of control of many.