The plan for covering the state employee members of the state employees' retirement system under the old age and survivorship provisions of Title II of the federal social security act as amended, required by RCW 41.48.050 as amended by section 5, chapter 4, Laws of the extraordinary session of 1955, approved by the state employees' retirement board of the state employees' retirement system on the 1st day of August, 1955, and approved by the governor of the state of Washington on the 16th day of August, 1955, is hereby approved.