University plans to convert Botanical Garden and Observatory areas into real estate projects designed to help meet the housing shortage problem will face their final test tomorrow night at 8 o'clock, when the Cambridge Planning Board will hold an open meeting in the City Hall to consider the Corporation's request for rezoning of the district.

If the Board okays the change in the zoning rules, the University will, providing that no objection is heard from the City Council, be able to begin work on the ground. Speculative plans for the dwellings call for one and four-family houses, distributed at a top average of 28 families to each of the seven acres of land available.