The Cork Trees. Along the road which follows the meadow south from the Administration Building is a stand of large trees -

Transcription

1 their The Cork Trees Along the road which follows the meadow south from the Administration Building is a stand of large trees - green flowers tinged with pink attracting bees in the late spring, the yellow leaves adding a gay note in the fall, and the gnarled open branches making interesting patterns against the snow in winter. The deep green foliage with pinnately compound leaves may suggest walnut trees, but their rough furrowed bark and dark blue-black berries identify them as Asiatic Cork trees or Phellodendrons. These trees belong to the Rutaceae, the family to which the orange and other citrus fruits belong, and like them they have leaves which are aromatic when bruised. The glands which produce these volatile oils can be seen with a magnifying glass as clear dots along the margins of the leaf. The Phellodendron trees are dioecious, having male and female flowers on separate trees and the flowers of both sexes, small and green with varying amounts of pink, are borne on panicles at the ends of the branches. In the flowers of one of the species, Phellodendron chinense, the green petals are noticeably streaked with rose and the densely flowered panicles are quite decorative. Inside the female flower the five united carpels are borne on a short stalk (gynophore) of glandular tissue which produces the nectar. This glandular area also appears beneath the rudimentary carpels in the male flower and in other genera of the family may appear as a disc or ring. In autumn the Phellodendron leaves turn a light clear yellow ; they fall quickly, leaving in the female trees bunches of black fruit hanging from the ends of the branches like small grapes. These fruits have a strong aromatic odor and contain five or six dark seeds. The fruits stay 162 on the trees most of the winter, providing food for starlings, robins, and other birds. The oldest of the Cork trees in the Arnold Arboretum is an Amur Cork tree, Phellodendron amurense, with gnarled and bent trunk, the thick branches spreading from about four feet above the ground. Here and there on the ground are exposed

2 163 large flat areas of woody root. The light grey bark is thick and furrowed, and although the tree gives the appearance of age, it is age accompanied by strength and grace. This patriarch of the group came as a seed from the Imperial Garden of St. Petersburg, Russia, and was planted here September 14, 1874, two years after the beginning of the Arboretum. Next to it stands another tree which was grafted from a piece of the first tree in November 18, This species is originally from northeast Asia, and gets its name from the great Amur river of that area. There are several Chinese cork trees, P. chinense, in the Arboretum collection. In parts of China the bark of this tree is called Huang-po and is used as a general remedy. One of these trees was grown from seed collected by Ernest H. Wilson in 1908 during his travels in China. The seed was from Western Hupeh, and Wilson described the area in his book, A Naturalist in Western Asia: "In the gorges the main river is joined by numerous lateral streams, branches of which flow through glens of wondrous beauty. These riverlets in winding their way usually fill nearly the entire bed of the glen and are bounded by walls of cliff from 300 to 1000 feet sheer. Waterfalls are numerous and wherever it is possible vegetation is rampant." In 1919 Wilson became Assistant to the Director of the Arboretum and later he was made Keeper (his own term) under Oakes Ames. The Arboretum has several examples of the Lavalle Cork tree, P. Lavallei. Two are from seed collected in Azuma, Japan, in 1905, by John George Jack, Assistant Professor of Dendrology at the Arboretum. The third, planted in 1919, is from seed collected by Wilson in Tokyo. Two of the Sakhalin Cork trees (P. sachalinense ) in the Arboretum are grafts made in 1919 of a tree which came from Germany in 1905 and is no longer living. The third Sakhalin Cork tree is a small tree, a comparative newcomer, raised from seed sent from the University of Tokyo in The name Sakhalin is from the name of an island north of Japan; the species is native there, in Korea, northern Japan, and western China. Another tree of this species which grew for some years in the Arboretum but is no longer living was grown from seed sent by William Smith Clark, president of Massachusetts Agricultural College, from Hokkaido in northern Japan in Clark went to Japan to establish an agricultural college at Sapporo, and while he was there he sent back seeds of many native trees and shrubs. Among these were the tree lilac (Syrin-

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5 166 ga reticulata), the Sakhalin Cork tree, the evergreen Bittersweet (Euonymus radicans var. vegeta) and others. The Pearfruit Cork tree (Phellodendron piriforme), is from seed received from the Botanical Institute of Leningrad, Russia, and was planted here in A graft of this tree is in the collection also. The two comparatively small trees of the Japanese Cork tree (Phellodendron japonicum) came as seed from the Botanic Garden, Berlin-Dahlen, Germany, in However, this species was represented much earlier in Cambridge, Massachusetts, by a tree now dead about which John Singer Sargent wrote in Trees and Shrubs, "It was raised before 1870 in the Botanic Garden of Harvard University at Cambridge, from seed from the Imperial Garden at St. Petersburg and probably collected by Maximowicz in Japan." C. J. Maximowicz was chief botanist at the Imperial Botanic Garden in the nineteenth century. he travelled in Japan and accumulated a large Japanese plants. From 1860 to 1864 collection of In addition to far and romantic places, the Cork collection represents the work of a large number of anonymous men who collected fruit and seeds and kept careful records, men who planted the seeds or grafted young cuttings on to sturdy rootstocks, men who tended the young plants from germination until they were ready to be put individual tree has a number and a filing card, and a record is kept of its growth until it dies. Recently a study was made of Phellodendron seeds. Groups of one hundred seeds were planted under varying conditions to determine the best method of germination. And at the Case Estates in Weston, Massachusetts, there are several young Cork trees which were started within the past few years at the Arboretum greenhouse as seeds. Some of the seeds came out in the Arboretum. Each from the Botanical Garden at the University of Bucharest, others came from England, Germany, and Russia. After a year or two at the greenhouse and at the nursery, they were transferred to Weston, where they are now young trees up to the Arboretum is assured of re- old and die. seven feet high. In this way placements when the present trees grow HELEN ROCA-GARCIA ~ Backing: Phellodendron amurense. Photo: H. Howard. Facing: Malus sargentii. Photo: H. Howard.

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