Cal. Gov. Code § 9022

At the day and hour appointed for the assembling of any regular session of the Legislature, the President of the Senate, or in case of his absence or inability, the senior member present, shall take the chair, call the members and members elect to order, and have the secretary call over the senatorial districts, in their order, from which members have been elected at the preceding election. As the districts are called the members elect shall present their certificates, take the constitutional oath of office, and assume their seats. If a quorum is present, the Senate may then elect its officers.