Note 4 — PETER KALM’s TRAVELS.
Johann Reinhold Forster translation
On many trees in the woods of this country, either on one of the sides, or in the middle of a branch, or round a branch, are greater or lesser knobs or excrescences. Sometimes there is only a single one in a tree. In the size there is a considerable difference, for some of these knobs are as big and bigger than a man’s head, others are only small. They project above the surface of the tree, like a tumor. Sometimes a tree was quite covered with them. They do not ly on one side only, but often form a circle round a branch, and even round the stem itself. The trees which have these knobs are not always great ones, but some not above a fathom high. The knobs commonly consist of the same parts as the wood itself, and look within like curled wood. Some of them are hollow. When a knob on a little tree is cut open, we commonly find a number of little worms in it, which are sometimes also common in the greater knobs. This shews the origin of the knobs in general. The tree is stung by insects, which lay their eggs under the bark, and from the eggs worms are afterwards hatched. They occasion an extravasation of the sap, which gradually condenses into a knob. Only the trees with annual deciduous leaves have these knobs, and among them chiefly the oak, of which again the black and Spanish oak have the greatest abundance of knobs. The ash trees, (Fraxinus excelsior) and the red maple (Acer rubrum) likewise have enough of them. Formerly the Swedes, and more especially the Finlanders, who are settled here, made dishes, bowls, &c. of the knobs which were on the ash-trees. These vessels, I am told, were very pretty, and looked as if they were made of curled wood. The oak-knobs cannot be employed in this manner, as they are commonly worm-eaten and rotten within. At present the Swedes no longer make use of such bowls and dishes, but make use of earthen ware, or vessels made of other wood. Some knobs are of an uncommon size, and make a tree have a monstrous appearance. Trees with knobs are very common in the woods of this country4.