Dispositions of property in trust for the purpose of the perpetual care, maintenance, improvement or embellishment of cemeteries or private burial lots in cemeteries, and the roadways, lawns, hedges, walks, fences, monuments, structures and tombs in such cemeteries or on such private burial lots are permitted and shall be deemed to be for charitable and benevolent purposes. Such dispositions are not invalid by reason of any indefiniteness or uncertainty of the persons designated as beneficiaries, nor shall they be invalid as violating any existing rule against perpetuities. Nothing herein contained shall affect any existing authority of the courts to determine the reasonableness of the amount of such disposition. Any cemetery association may act as trustee of and execute any such trust with respect to lots, roadways, lawns, hedges, walks, fences, monuments, structures and tombs both within its own cemetery limits and outside of any cemetery under its control but within the county where such cemetery is located, whether or not such power is included among its corporate powers.