Civ. Code, § 724

(a) An accumulation of the income of property may be directed by any will, trust or transfer in writing sufficient to pass the property or create the trust out of which the fund is to arise, for the benefit of one or more persons, objects or purposes, but may not extend beyond the time permitted for the vesting of future interests.

(b) Notwithstanding subdivision (a), the income arising from real or personal property held in a trust forming part of a profit-sharing plan of an employer for the exclusive benefit of its employees or their beneficiaries or forming part of a retirement plan formed primarily for the purpose of providing benefits for employees on or after retirement may be permitted to accumulate until the fund is sufficient, in the opinion of the trustee or trustees, to accomplish the purposes of the trust.