characteristic shape of pruned Japanese garden trees resemble trees found naturally in savannah landscapes. This resemblance has been used to motivate the so-called Savannah hypothesis. Trees are sometimes constrained to bend, in order to provide shadows or better reflections in the water. Very old pine trees are often supported by wooden crutches, or their branches are held by cords, to keep them from breaking under the weight of snow. In the late 16th century, a new art was developed in the Japanese garden; that of , the technique of trimming bushes into balls or rounded shapes which imitate waves. According to tradition this art was developed by Kobori Enshū (1579–1647), and it was most frequently practiced on azalea bushes. It was similar to the topiary gardens made in Europe at the same time, except that European topiary gardens tried to make trees look like geometric solid objects, while sought to make bushes look as if they were almost liquid, or in flowing natural shapes. It created an artistic play of light on the surface of the bush, and, according to garden historian Michel Baridon, "it also brought into play the sense of 'touching things' which even today succeeds so well in Japanese design." The most common trees and plants found in Japanese gardens are the azalea (), the camellia (), the oak (), the elm (), the Japanese apricot (), cherry (), maple (), the willow (), the ginkgo (), the Japanese cypress (), the Japanese cedar (), pine (), and bamboo (). Fish The use of fish, particularly (colored carp), or goldfish as a decorative element in gardens was borrowed from the Chinese garden. Goldfish were developed in China more than a thousand years ago by selectively breeding Prussian carp for color mutations. By the Song dynasty (960–1279), yellow, orange, white and red-and-white colorations had been developed. Goldfish were introduced to Japan in the 16th century. Koi were developed from common carp (Cyprinus carpio) in Japan in the 1820s. Koi are domesticated common carp that are selected or culled for color; they are not a different species, and will revert to the original coloration within a few generations if allowed to breed freely. In addition to fish, turtles are kept in some gardens. Natural environments in the gardens offer habitats that attract wild animals; frogs and birds are notable as they contribute with a pleasant soundscape. Aesthetic principles The