The sorrel tree, or sour-wood (_Oxydendrum arboreum_, DC.) belongs among the heaths. Its vivid scarlet autumn foliage is its chief claim to the admiration of gardeners. In spring the little tree is beautiful in its bronze-green foliage, and in late July and August it bears long branching racemes of tiny bell-shaped white flowers. This multitude of little bells suggests the tree's relationship to the blossoming heather we see in florists' shops.
The leaves give the tree its two common names: they have a sour taste, resembling that of the herbaceous sorrels. The twigs, even in the dead of winter, yield this refreshing acid sap, that flows through the veins of the membranous leaves in summer. Many a hunter, temporarily lost in Southern woods, quenches his thirst by nibbling young shoots of the sour-wood.
After the flower comes a downy capsule, five-celled, with numerous pointed seeds. The leaves are not unlike those of a plum tree except that they attain a length of five to seven inches. In the woods from Pennsylvania, Ohio, and Indiana, southward to Florida, Alabama, Louisiana, and Arkansas this tree ranges, and we often see it in cultivation as far north as Boston. It grows to its largest size on the western slopes of the Big Smoky Mountains in Tennessee, attaining here a height of sixty feet. In cultivation it is one of the little, slender-stemmed, dainty trees, beautiful at any season. It is the sole representative of its genus in the world, so far as botanists know.
The silver bell tree (_Mohrodendron tetraptera_, Britt.) earns its name in May when among the green leaves the clustered bell flowers gradually pale from green to white, with rosy tints that seem to come from the ruddy flower-stems. A "snowdrop tree" may be eighty feet in height, in the mountains of east Tennessee and western North Carolina, but ordinarily we see it in gardens and parks as a delicate, slender-branched tree, that stands out from every other species in the border as the loveliest thing that blooms there.
Not a moment in spring lacks interest if one has a little mohrodendron tree to watch. For weeks the ruddy twigs grow ruddier by the opening of leaf and flower buds; then comes the slow fading of the flowers, when sun and rain seem to work together to bleach them into utter purity of color and texture. Gradually the white bells fade and a queer little green, tapering seed-case enlarges and ripens. Through the late summer these pale green fruits are exceedingly ornamental as the leaves turn to pale yellow.