ARBORETUM, a place where trees and shrubs are cultivated for scientific, ornamental or other educational purposes ; that por tion of a botanical garden used for woody plants. There are many such collections of hardy plants in cities and private parks. Rich men often spare neither pains nor money to get important col lections to adorn their estates, many of which have later been given to cities to be used as public parks. When properly main tained they make creditable arboretums. The modern arboretums contain plants as specimens or collections arranged according to some definite method—it may be systematic relationships, or com mercial uses, or perhaps, to show ecological adaptations. The en tire field of possibilities is seldom covered by any one arboretum, but each one specializes in a few projects for which it is particu larly equipped or well situated.
As early as the middle of the i6th century Rene du Bellay of Touvoys, France, in co-operation with Pierre Belon made a good collection of trees and brought into France seeds of exotic species from western Asia. This collection long remained the richest and most beautiful in France or perhaps the world. About 1720, Duhamel du Monceau, head of the French Marine, and a scientist, gathered plants from all over Europe and North America to plant on his two estates. The plants were classified, arranged and planted in a methodical manner resulting in what might be called the first arboretum made with scientific purposes. From his expe rience with the collection, du Monceau wrote and published in a book on characteristics and cultivation of trees and shrubs. This collection of plants and the publication had a great influence on study and early distribution of imported plant species. Many of these imported types can still be found in France.
One of the most complete arboretums in the world is that at Kew, England, in the Royal Botanical Gardens. It had its begin nings as far back as 1762 though it was not thrown open to the public until 1841. To the latter date the ground, not exceeding 1 iac., had been held as a private estate by members of the royal family. In 1845 the pleasure grounds and Royal Gardens at Kew, occupied by the king of Hanover, were given to the nation and placed under the care of Sir William Hooker for the purpose of establishing an arboretum. Hooker and his son, Sir Joseph, kept steadily at the task until the gardens and arboretum were among the finest and most complete in the world. The arboretum mo nopolizes a large portion of the entire garden (288ac.) with trees and shrubs representing some 4,500 species and varieties. In ad dition to the arboretum at Kew, important collections of trees and shrubs in Great Britain are those at the Royal Botanic Gardens in Edinburgh and at the Glasnevin Garden in Dublin, and a small select collection at Oxford. On the continent of Europe the clas sical example is the Jardin des Plantes in Paris. Here the gardens are very formal and make a striking effect.
In the United States the Arnold arboretum at Boston ranks with Kew in size and completeness. This institution had its be ginnings in 1869 when James Arnold left in trust $Ioo,000 to be used for the promotion of agriculture or horticulture. Through an agreement made with Harvard college officials in 1872, the Arnold bequest was used together with a 125ac. tract of land, be queathed by Benjamin Bussey, for the establishment of a tree garden. Charles Sprague Sargent was made the first director. He held the position until his death in 1927. During this time he made a notable arboretum, the best in the United States and ranking favourably with the best in the world. Sargent left $io, ooc to the Arnold arboretum to be used with accumulated interest 200 years hence, at which time it will amount to millions of dollars. Its 26oac. are planted with 6,536 species and varieties of trees, shrubs and vines belonging to 339 genera. Of these, 2,418 species or varieties are exotic, coming particularly from Japan, China, Siberia and the Himalayas. The Arnold arboretum by agreement is a part of the regular park system of Boston, but, being under the management of a great university like Harvard, it has an aspect differing entirely from an ordinary park.
Among the other most outstanding arboretums in the United States are the Missouri Botanical garden in St. Louis, Mo., the Morton arboretum near Chicago, Ill., and the Hilland gardens in Rochester, New York. Three million dollars have been appropri ated for the establishment of the Boyce Thompson arboretum in connection with the Boyce Thompson Institute for Plant Re search, Yonkers, New York. The Boyce Thompson arboretum combines a large collection of trees and shrubs with a great plant research institute thus utilizing the greatest range of possibilities of an arboretum. The National arboretum at Washington, D.C., has received an appropriation of $300,000 from the Government for the purchase of lands. Further appropriations will be given for buildings and maintenance as the needs arise. It will be a laboratory for the plant scientists of the U.S. department of agriculture. The California Botanical garden at Los Angeles, Calif., has received a gift of 2,0o0ac. of land, part of which will be used for the arboretum and part of which can be sold for capital and maintenance.
The tendency of recent times is to manage arboretums so as to make them serviceable to the people. To serve most people an arboretum must have a scientific, an economic and a cultural as pect. On the scientific side the arboretum furnishes all types of hardy plants for the systematic botanist, the plant pathologist, the plant physiologist, the plant-breeder and the entomologist. From this will come a thorough study of diseases and rational control measures; a better knowledge of soil requirements and cultural methods ; many new plant hybrids from controlled cross—breeding; and new methods of combating insect pests. The nurserymen and horticulturists look upon an arboretum as a place where plants are tested and displayed for the purpose of showing their eco nomic possibilities. In this way the forester selects the species which fulfil specific needs for paper pulp, trees for hardwood lum ber, etc. The nurserymen select from the arboretum species that they can fit into the landscape for the increasing demands of the public. Lastly, the public in general looks upon an arboretum as an unusually fine park, a place to go when in need of peaceful rest and a place that offers a chance to increase one's knowledge about nature. (See also BOTANIC GARDEN, FORESTRY and HORTI CULTURE.) (P. W. Z.)