. The beauties of nature and the wonders of the world we live in. Natural history; Physical geography; Astronomy. 142 THE BEAUTIES OE NATUEE chap. Sycamore, space would be wasted, and it is better that they should expand at once, so soon as their stalks have carried them free from the upper and inner leaves. In the Black Poplar the arrangement of the leaves is again quite different. The leaf stalk is flattened, so that the leaves hang. Fig. 16. — Acer platanoides. vertically. In connection with this it will be observed that while in most leaves the upper and under surfaces are quite unlike, in the Black Poplar on the contrary they are very similar. The stomata or breathing holes, moreover, which in the leaves of most trees are confined to the under surface, are in this species nearly equally numerous on both.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Lubbock, John, Sir, 1834-1913. New York, London, Macmillan and Co.