The Name thing.

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does usufruct carry an obligation to exercise its power for the benefit of the beneficiary?

Latin: the beneficiary of a trust.

Modern trust law prefers the word beneficiary but the older cases refer to the older Latin term of cestui que trust.

"A trust is an equitable obligation binding a person (who is called a trustee) to deal with property over which he has control (which is called the trust property) for the benefit of persons (who are called beneficiaries or cestui que trust) of whom he may himself be one, and anyone of whom may enforce the obligation. Any act or neglect on the part of a trustee which is not authorised or excused by the terms of the trust instrument, or by law, is a breach of trust."

Six pages here

http://www.cfhlaw.com/attorneys/anthony_j_correro.htm :

He has advised clients in an immense variety of securities, mergers and acquisitions and corporate finance deals, ranging in size from $3.1 billion to $100,000, including the $3.1 billion sale of First Commerce Corporation to Bank One; the purchase of Sugarland Bank by MidSouth Bancorp for $1.2 million; the $500 million purchase of Zapata Corporation by Tidewater, Inc.; the sale of VitaRx to McKesson Corporation for $62 million; Amedisys's acquisition of HMR Acquisition, Inc.; public offerings of oil and gas interests for a single client aggregating $1 billion and the private offering of oil and gas interests for a single client of $100,000; as well as initial public stock offerings for several companies.

Andy wrote the Louisiana Bank Holding Company Law, which ushered statewide banking into Louisiana, and since then has handled over 30 bank mergers in the state, representing both buyers and sellers.