Resistance to disease and insects is a taxonomic and an economic character of much importance. Thus there are great variations among varieties in resistance to peach-yellows, brown-rot and leaf-curl, the three commonest diseases of this fruit in New York, as there is also in resistance to San Jose scale, the worst insect-pest of the peach in this region and to the peach-borer, the commonest. These examples are multiplied in the discussions of varieties, pains having been taken in the peach-orchards at this Station to determine the relative resistance of all varieties to the pests of this region. But little attention need be paid to the old bark on peach-trees, since in all varieties it is much the same and is unimportant to the cultivator. The bark of all varieties varies in color on different soils and is always of a lighter hue in cold than in warm regions, in dry than in wet situations. The branches and branchlets of varieties are very characteristic. The length, thickness, direction, rigidity and the branching angle are all stable characters of varieties, changing but little with differences in soil and climate. The length of the internode is important as is also color, smoothness, amount of pubescence, size and appearance of the lenticels, and the presence of excrescences,--though all are exceedingly variable. Both leaf-buds and fruit-buds are used in separating groups of peaches but are too nearly alike in the several groups to be of aid in distinguishing the varieties of any group. Fruit-buds are borne in pairs on the wood of the previous year with a leaf-bud separating the members of the pair. The only characters of buds worth noting are size, shape, color and the angle at which the buds stand out from the branches. After the fruits, the leaves offer the best means of determining groups and varieties of peaches. Leaves are variable, it is true, but usually within limits quite easily set, since the conditions causing the variations are easily discovered. The most usual ones are extremes in soil, moisture, light, heat and the age of the wood upon which the leaves are borne. Much care has been taken to illustrate as accurately as possible the leaves of the varieties given color-plates in this text, size and form being reproduced exactly and color as nearly as color-plate printing permits. Leaf-size and leaf-form are the first characters of the foliage to study in determining varieties. The former varies somewhat in accordance with the conditions named in the foregoing paragraph but the shape of the leaf changes but little. Fortunately for the student of varieties, leaves differ most in relative length and breadth so that the shape may be accurately indicated by figures which are used in most of the descriptions in _The Peaches of New York_. Comparisons of the bases and the apices of leaves of different varieties often show distinguishing marks.