PREFACE. The closing decades of the nineteenth century have seen great changes in the principles of citrus fruit culture in America. Twenty years ago the amount of fruit pro- duced was comparatively small, now the industry has at- tained a place among the large horticultural industries of this country. Then, at most, a few hundred boxes of fruit were produced annually now the crop is counted not by hundreds but by millions of boxes. The pomelo was scarce- ly known and the lemon was a fruit imported almost en- tirely from the Old World. Then, the means of transportation closed many a desirable tract of land through which the railroad now runs and from which large quantities of fruit are now shipped. Then, the methods of combating insects and fungous diseases were less perfectly under stood than now. In those days, the fertilizers applied to the soil were mostly made at home, now the nitrogen, phos- phorus and potash, deemed so essential for the production of first-class fruit, in many...