"And now," said Miss Harson, when the children were wondering if that were the end, "we have come to the most interesting tree of the whole species--the aspen, or trembling poplar. It is a small, graceful tree with rounded leaves having a wavy, toothed border, covered with soft silk when young, which remains only as a fringe on the edge at maturity, supported by a very slender footstalk about as long as the leaf, and compressed laterally from near the base. They are thus agitated by the slightest breath of wind with that quivering, restless motion characteristic of all the poplars, but in none so striking as this. 'To quiver like an aspen-leaf has become a proverb. The foliage appears lighter than that of most other trees, from continually displaying the under side of the leaves.