In any action for specific performance or for damages brought by a proprietor of any land under the operation of this Act against a person who has contracted to purchase the land not having notice of any fraud or other circumstances which according to this Act would affect the right of the vendor, the certificate of title of the proprietor shall be held to be conclusive evidence that the proprietor has a good and valid title to the land for the estate or interest mentioned or described in the certificate of title, and shall in any such action entitle the proprietor to a decree for the specific performance of the contract.