Section 25. Subject to section twenty-seven the trustees may sell and convey, in the name of and for the commonwealth, to any professor, instructor, teacher or employee of said university, or to any society, association or fraternity established thereat, land owned by the commonwealth in Amherst or Hadley. Not more than one acre shall be so sold and conveyed to any one such person or organization. Such conveyances shall contain necessary restrictions and conditions.