Lettuce: stems erect, solitary, upper conical, inflorescences branched, the color of all the stems and branches of the white, basal leaves and lower stem leaves are larger, undivided, the base of the heart-shaped or arrow-shaped half-embracing stems, the edge of the undulate or serrulate. Lettuce (in the case of curly lettuce): the leaves are rounded, clasped and rolled up with each other into a kale-like leaf ball, the leaves are divided or undivided, and the involucral bracts are 3-5 layers, thin in texture, and arranged in an imbricate pattern.