What is the shape and function of sweet chestnut cotyledon?

Sweet chestnut leaf: it is blue all over, with sharp "teeth", and the shape around it is like small thorns, and the veins on the leaf are also clearly visible.

Chestnut tree, deciduous tree, the fruit is called chestnut, and the nuts are sweet and edible. Wood is solid and can be used in buildings and utensils, and bark can be used for tanning and dyeing. Chestnut trees are used in gardens. Chestnut trees are planted as excellent landscape trees in landscaping around the world, and are usually transplanted with half-crown width. Location: Shandong, Anhui, Jiangsu, Hebei, Henan and other places. Chestnut, peach, apricot, plum and jujube are also called "five fruits".