Lotus plays an important role in Jinan people's life. In the use of lotus, Jinan has some special customs. Among them, the most interesting is the blue tube drink. In ancient times, when the lotus flowers in Daming Lake were in full bloom, some officials and scholars often went to the lake for the summer, cut off the big lotus leaves in the lake, filled them with wine, and then stabbed them in the center with a hairpin to make them communicate with the hollow lotus stems. People drink water from the end of the lotus root. This is the beautiful talk "Bitong Drink" handed down by literati in Tang and Song Dynasties.

The drinking method with lotus leaf as cup first appeared in Cao Wei era. At that time, some people gave a banquet to drink, taking lotus leaves as cups, sticks through petioles, and handles as pipes to drink. Lotus leaves used to hold wine are called "lotus cup", "lotus lamp" and "blue tube cup". Because the stem is bent like a trunk, it is called "elephant trunk cup".

Morphological characteristics of lotus leaves;

The blades are mostly folded into semicircular or fan-shaped, and when unfolded, they look like a round shield, with a diameter of 20 to 50cm, and are whole or slightly wavy. The upper surface is dark green or yellow-green, rough; The lower surface is light taupe and smooth, with 22 thick veins radiating from the center to the periphery, and there are prominent petiole residues in the center. Fragile and easily broken. Slightly fragrant, slightly bitter. It is best to have big, clean and green leaves.

The stems of lotus leaves are green and covered with small thorns; If you break the stem of the lotus leaf, there will be many connected filaments on the stem. Numerous micron-sized waxy papillae structures are attached to the surface of lotus leaves. The contact area between the lotus leaf surface and water droplets or dust is very limited, so the water droplets roll on the leaf surface and take away the dust. Water will not stay on the surface of lotus leaves.