Horticulturally, hardiness is ability to withstand cold. Obviously, hardiness is of utmost importance in characterizing the value of a variety to the pear-grower, and degree of hardiness is of some use in identifying pears. Bartlett and Beurré Bose are relatively tender to cold, Tyson is hardy, and Flemish Beauty is very hardy. Less important, but still of some importance, is the ability to withstand heat, a character possessed in varying degrees by varieties of pears. Productiveness, age of bearing, regularity of bearing, certainty of bearing, and longevity are constitutional characters that must be noted in full descriptions. All help to determine the value of a variety, and all aid more or less in classification. For most part, these are inherent characters and are influenced but little by environment. The degree of susceptibility of a variety to fungous diseases and insect pests is a valuable cultural character, but has little use in identifying or classifying pears. There are great variations in varieties of pears to the dreaded pear-blight: Bartlett, Beurré Bose, Beurré d'Anjou, and Clapp Favorite are among the varieties most susceptible; Kieffer, Seckel, and Winter Nelis are among those least susceptible to blight. Kieffer and related hybrids are somewhat immune to San Jose scale, but are very susceptible to psylla. Flemish Beauty and White Doyenné are so badly attacked by the scab-fungus that it is almost impossible to grow them in eastern America. Some of these constitutional characters are much modified by care and environment, as all are more or less. Care and local environment often make it possible to grow varieties in special localities, although some varieties are inherently adapted to a greater number of diverse conditions than others. Bartlett, Seckel, and Kieffer have in common as one of their most valuable characters adaptability to a great diversity of soils and climates. _Trunk and branch._--The trunk does not count for much in descriptions of varieties. The height of the trunk usually depends on the whims of the pruner. Whether _stout_ or _slender_ is sometimes noteworthy. The bark may be _smooth_ or _shaggy_. Color of bark is often a valuable diagnostic character, especially in young trees. Many if not most varieties of pears can be identified in nursery rows by an expert nurseryman from the color of the bark. Seckel, Sheldon, and Beurré d'Anjou have remarkably distinctive color as young trees.