Trees used as fillers for apples should have two important characteristics; they should be rapid, vigorous growers and should come into bearing at a very early age. Two kinds of fillers are available, those of the same species, which may be either dwarf or standard trees, and those of a different species, of which peaches and plums, and possibly pears, are the best adapted. Dwarf trees may be dismissed from our plans with the statement that they have rarely proved profitable under ordinary conditions, as they are much more difficult to grow than standards and when grown they have but few advantages over them. The varieties of standard apples which are advisable as fillers have been indicated in Chapter II. The use of peaches and the Japanese plums, both of which make excellent fillers because they grow rapidly and come to heavy bearing quickly, is limited to their soil and climatic adaptation. They are adapted to the lighter phases of soil and the more moderate climates and under other conditions are impracticable. On heavier soils and in more rigorous climates the European plums and the more rapid and early bearing pears, such as the Keiffer, make fairly good fillers. On the whole, the writer is inclined to advise the use of fillers in the general farm orchard. Quicker returns from an investment of this nature, which is usually heavy and which at best must be put off several years, are very important. Under careful and intelligent management the objections to their use are easily overcome. SPACING AND ARRANGEMENT OF TREES.--The distance apart of planting depends on the variety planted. Close headed, upright growing trees may be planted closer together than spreading varieties. Some varieties grow larger than others, and the same variety may vary in size on different soils. It is seldom advisable to plant standard apple trees in the latitude of New York closer than thirty feet, or farther apart than fifty feet. Trees of the nature of Twenty Ounce and Oldenburg (Dutchess) should be planted from thirty-two to thirty-six feet apart, while Baldwins, Rhode Island Greenings, and Northern Spies represent the other extreme and will require forty, and sometimes fifty feet of space. The method and thoroughness of pruning influences the size of trees greatly, and hence the distance at which It is necessary to set them. Varieties top worked on other stocks have a tendency to grow more upright and may be set closer together. It should be remembered in this connection that the roots of a tree extend considerably beyond the spread of the branches. From thirty-five to forty feet is a good average distance and trees should be trained so as to occupy this space and no more. Where fillers are used the latter distance is best, as the twenty feet apart at which the trees will then stand is close enough for any standard variety.