the property, and the university, as trustee, is directly responsible for the development, maintenance, and operation of the Arboretum; the City retains responsibility for water fountains, benches, roads, boundaries, and policing. The annual operating budget is largely derived from the endowment, which is based primarily on private philanthropy and managed by the university. Other income is obtained through granting agencies and contributors. All Arboretum staff are University employees. Location The Hunnewell Building (which includes the Visitors Center and the Horticultural Library) is located at the main Arborway Gate. This entrance can be accessed on Massachusetts Route 203, a few hundred yards south of its junction with the Jamaicaway. Public transportation to the Arboretum is available on the MBTA Orange Line to its terminus at Forest Hills Station and by bus (#39) to the Monument in Jamaica Plain. The Arboretum is within easy walking distance from either of these points. The Arboretum's southwest gate is very close to the turn between Weld and Walter Streets on the #51 bus line between Cleveland Circle/Reservoir and Forest Hills. The Centre Street entrance, across from Whitcomb Ave and Westchester Road, is served by the #38 bus. The Arboretum occupies 281 acres in the Jamaica Plain and Roslindale sections of Boston. In 1938, the total area was given as 265 acres, a figure that was reported for decades until being corrected. The Arboretum contains four notable hills: Bussey Hill, Peters Hill, Hemlock Hill, and Weld Hill. Of these, Peters Hill is the tallest at . Climate Average yearly rainfall is ; average snowfall, . Monthly mean temperature is ; July's mean temperature is ; January's is . The Arboretum is located in USDA hardiness zone 6b (). Collections (as of February 2015) At present, the living collections include 14,980 individual plants (including nursery holdings) belonging to 10,117 accessions representing 3,924 taxa; with particular emphasis on the ligneous species of North America and eastern Asia. Historic collections include the plant introductions from eastern Asia made by Charles Sprague Sargent, Ernest Henry Wilson, William Purdom, Joseph Hers, and Joseph Rock. Recent introductions from Asia have resulted from the 1977 Arnold Arboretum Expedition to Japan and Korea, the 1980 Sino-American Botanical Expedition to western Hubei Province, and more recent expeditions to China and Taiwan. Comprehensive collections are maintained and augmented for most genera, and genera that have received particular emphasis include: Acer, Fagus, Carya, Forsythia, Taxodium, Pinus, Metasequoia,