I just bought a tree in bonsai show. It's labeled as Japanese Elm. After searching the internet for more information, I came to conclusion that it 's not a Japanese Elm (Zelkova serrata)
It has groups of leaves. Each group has 3 or 7 leaves (picture). Each leaf is about 1 in long and 1/2 in wide with toothed margin. The upper surface of leaf has dark green and lower surface has light green. 2 groups of leaves are opposite each other and other groups of leaves emerged from the branch with rectangle direction compared with their neighbor (like Japanese maple or pomegranate way).
And the new branches will emerge from the base of the groups of leaves (picture)
What tree do you think? Thanks. Bonhe