In 1918 a fire, commencing in the furnace room, caused damage to the conservatory's Potting Room and adjacent Dome Room. Repairs were made as needed. Another fire struck the Conservatory in 1918, causing the roof to partially collapse. Depression Era decline During the Depression, the Conservatory of Flowers, due to apparent lack of maintenance, was in poor condition. The Park commissioners instructed the superintendent of Parks to close the Conservatory of Flowers in 1933 and construct proper barricades to prevent possible injury to citizens. The woodwork, foundations, girders, posts, and various structural members became rotted and decayed to such an extent that certain portions of the conservatory were reported to be in danger of falling and potentially causing great injury. Post-War era In August 1946, the Conservatory of Flowers was painted and reglazed. A new electrical system, which allowed automatic control of the heating system for all of the conservatory, was installed in 1948. New piping was installed in 1949. A new water supply was installed in 1956. In 1959, the original doors at the wing entrances were replaced with plate-glass windows and concrete panels. That same year, the lower ventilators at the building's perimeter were removed, and concrete panels, cast in the profile of the ventilators, were installed. This unfortunately seriously compromised the building's natural ventilation system. A few minor repairs were made in 1962 and 1965. The Conservatory of Flowers was added to the National Register of Historic Places on October 14, 1971. It had previously been named a California Historic Landmark on September 1, 1970, and would be designated a San Francisco Landmark on December 4, 1972. A major rehabilitation project took place between 1978 and 1981. Work included the removal of all interior and exterior caps of the arches for visual inspection and probing, in order to detect pockets of wood rot. The portions of arches showing surface wood rot were treated with 'Git-Rot', a wood preservative. The caps that remained in good condition were salvaged and reinstalled. Building evidence suggests that the exterior surfaces of the arches were originally fitted with copper flashing. The flashing was secured onto the arches and covered by the wood caps. In most locations that were inspected, the flashing had been removed, leaving only short remnants at random locations. The flashing was rolled up and taken away during the 1982 restoration effort. The flashing was an effective method of preventing