They have rigid, entire leaves with one edge turned toward the zenith. most of them secrete resinous gums, whence they called gum trees, and their timber is of great value. Eucalyptus Globulus is the blue gum; E. Aigantea, the stringy bark: E. Amygdalina, the peppermint tree. E. Gunnii, the tasmanian cider tree, yields a refreshing drink from wounds made in the bark in the spring. Center species yield oils, tars, acids, dyes and tans. It is said that miasmatic valleys in algeria and Portugal, and a part of the unhealthy roman Campagna, have been made more salubrious by planting groves of these trees.