Old Ginkgo tree at Maldegem (Belgium): Noordstraat 15, front garden of former house of Victor deLille.
c. 1840, female, with chichi.
The Ginkgo can produce peg-like structures (chi-chi = nipples, sort of "aerial" lignotubers) along the trunk and branches that can grow into the ground and form roots as well as leafy branches above because of the embedded vegetative buds, which is characteristic for the Ginkgo. The chichi (Chinese: zhong ru) seem to be connected to traumatic events, environmental stress and individual properties of a tree. It is seen with old, but also with younger trees.
The girth of the trunk of the older trees may become large because of secondary growth. The tree usually loses its central leader and gives rise to several vertical trunks ("basal chichi") that keep reaching great heights. These socalled lignotubers can also be observed on this tree.
It is thought the chichi, its resistance against diseases, its adaptability and individual properties of the tree etc. contribute to the long history of the survival of the Ginkgo.
More info on my website The Ginkgo Pages: http://www.xs4all.nl/~kwanten/ (less info)