Sagittarius sagittarius, also known as arrowhead, arrowhead, swallowtail grass, white chestnut, etc., is a plant of Sagittarius in Alismataceae, and its fruit is edible and astringent. Sagittaria sagittata is rich in starch, protein, sugar, inorganic salts, vitamins B, C and trypsin. It is native to Central China and South China in China, and is born in shallow ditches, streams or paddy fields. Sagittarius grows in paddy fields, but its leaves are very special. When the leaves first grow, they are strip-shaped, and when they grow a little, they are arrow-shaped. Because of growing in paddy fields, strip-shaped leaves are often submerged in water. Arrow-shaped leaves have a long petiole, and the arrow-shaped leaves are lifted high above the water surface by the petiole. Why do sagittarius have two different shapes of leaves? Sagittarius usually grows in shallow water, and the leaves that have just begun to grow are often submerged in the water. Strip leaves can reduce the resistance in the water, especially when the water flows, it is not easy to wash away the small Sagittarius seedlings. With the growth of the plant, the leaves that stand out of the water are wider, which is conducive to receiving more sunlight. In this way, the leaves in water are different from those on water, which is beneficial to its growth in paddy fields, which is the result of long-term adaptation of plants to the environment. There is also a plant called Sophora japonica, which is a kind of plant that floats on the water and grows. This kind of plant is also very special. There are three leaves on each node of the stem. Two leaves are flat on the water surface, or inclined to the water, and the other leaves sink into the water. Submerged leaves change into roots, which can absorb nutrients in water like roots. The leaves of Sophora japonica are submerged in water, which not only changes their morphology, but also changes their functions. This is also the result of long-term adaptation of plants to floating life on water. In addition, there is a kind of plant called Ranunculus japonicus, which is rooted at the bottom of the water, and the leaves that grow out of the water are wider, while the leaves that sink in the water are split into many thin strips, which is also conducive to reducing resistance. Therefore, the leaves of plants growing in water are different from those on the water surface, which is the result of adapting to the aquatic environment.