When a tree is very old, yet still lives, sometimes the limbs are strangely twisted.

"The Island of Doctor Death and Other Stories" (1970), Orbit 7, ed. Damon Knight; reprinted in Gene Wolfe, The Island of Doctor Death and Other Stories and Other Stories (1980); reprinted in Gene Wolfe, The Wolfe Archipelago (1983); reprinted in Gene Wolfe, The Best of Gene Wolfe (2009)