A treatise on the law of trusts is a comprehensive legal text that provides an in-depth analysis and explanation of the law related to trusts. These texts typically cover the history and development of trust law, the types of trusts, the duties and responsibilities of trustees, the rights of beneficiaries, the creation and administration of trusts, the laws governing trusts, and the taxation of trusts. Some of the well-known treatises on the law of trusts include "Baker on Trusts" by Richard Baker, "Megarry & Wade: The Law of Real Property" by Charles Harpum, and "Scott on Trusts" by William Fratcher Scott.