英语时差：睡莲叶，伞叶树和葡萄树（上）

Look closely at a lily pad sometime and you’ll see that its shape is different from virtually any other leaf. With most leaves, the stem attaches to one edge of the leaf. You can see how lily pads are different from other leaves if you imagine an insect crawling up the leaf. On most leaves, the insect could climb directly from the stem onto the upper surface of the leaf. Not so with a lily pad. The stem of the lily pad – which connects the flower to the bottom of the pond — meets the leaf in the middle of its underside. An insect crawling up the stem of a lily pad would have to climb over the underside of the leaf before climbing out onto the top. In a pond, this leaf shape helps the leaf to float flat on the surface with the stem hanging straight down to the bottom.