Even a first grader knows quite a bit about trees, so this guessing game will have less immediate appeal than Guess What Grasses Do (KR, 1972) which introduced the novel (to most youngsters) concept that wheat, corn and other food plants are kinds of grass. But Darwin's flowing decorative silk screens keep the mood cheerful so that the text never seems forced even though scientific concepts are reduced to the simplest terms (""Leaves of trees do a very special job. They remove from the air the carbon dioxide. . .""). The examples of specific tree products -- chocolate, chewing gum and totem poles -- are similarly chosen to stimulate questions -- and at the right level they should catch on.