The several very different forms of Chinese cabbage, including bok choy, napa, and tatsoi, all stem from the same species of Brassica that gave us the turnip. B. rapa is one of the oldest cultivated plants, possibly bred first for its seeds, and now among the most important vegetables in Asia. The larger modern forms are mainly elongated heads weighing up to 10 lb/4.5 kg, and are distinguished from European cabbages by their prominent white midribs, less prominent light green leaves, and mildness. Their smaller relatives mizuna and mibuna form low, spreading clumps of long, narrow leaves, those of mizuna being finely divided and feathery. Tatsoi makes a rosette of rounded leaves. These small leaves do well as additions to Western salads; they tolerate storage and dressings better than more delicate lettuces.