Section 26. All restrictions on the use of land or construction thereon which run with the land subject thereto and are imposed by covenant, agreement, or otherwise, whether or not stated in the form of a condition, in any deed, will or other instrument executed by or on behalf of the owner of the land or in any order of taking shall be subject to this section and sections twenty-seven to thirty, inclusive, except (a) restrictions in leases, mortgages and other security instruments, (b) restrictions in orders of taking by the commonwealth or a political subdivision or public instrumentality thereof made before January first, nineteen hundred and seventy and (c) conservation, preservation, agricultural preservation, and affordable housing restrictions, as defined in section thirty-one which have the benefit of section thirty-two, and other restrictions held by any governmental body, if the instrument imposing such conservation, preservation, agricultural preservation, affordable housing or other restriction is duly recorded and indexed in the grantor index in the registry of deeds or registered in the registry district of the land court for the county or district wherein the land lies so as to affect its title, and describes the land by metes and bounds or by reference to a recorded or registered plan showing its boundaries. ''Governmental body'', as referred to in this section and sections thirty-two and thirty-three, means the United States or the commonwealth, acting through any of its departments, divisions, commissions, boards or agencies, or any political subdivision or public instrumentality thereof or any public authority or any quasi-public entity or any instrumentality created pursuant to chapter forty F, whether acting for its own account, or as agent or designee for or assignees of any private individual or private entity which has been required to place such restriction in its chain of title as a condition to receiving financial or other assistance from the United States or the commonwealth, acting through any of its departments, divisions, commissions, boards or agencies, or any political subdivision or public instrumentality thereof or any public authority or any quasi-public entity or any instrumentality created pursuant to said chapter forty F.

For the purposes of this section and sections twenty-seven to thirty, inclusive:—

1. ''Subject parcel'' or ''subject land'' means land upon which such a restriction is imposed.

2. ''Benefited land'' means land for the benefit of which such a restriction is imposed.

3. ''Public records'' shall be limited to records filed in the registries of deeds, probate courts and the land court and its registry districts.

4. A description of land shall be sufficient if it specifies the city or town in which the land lies and the place of record in the public records where there is a recorded or registered plan or instrument giving the boundaries of the land and identifies the land with reference to said plan or instrument and, if the land is registered, specifies the certificate or certificates of title thereof.

5. Restrictions may be deemed imposed as part of a common scheme if imposed of record on various parcels in such manner that each owner is entitled to enforce the restrictions against the other parcels, although there may be variations in the restrictions among the various parcels.

Unless the instrument imposing the restriction provides otherwise, it is to be presumed that a restriction imposed as part of a common scheme is enforceable for the benefit of any land only when such land either (a) is bounded by a street by which the subject parcel is bounded or (b) lies in a block surrounded by the same streets as the subject parcel, or (c) is contiguous to said block except for streets or ways.