Upon the receipt of such receipts from said county treasurers, it is the duty of the register of the state board of land commissioners to enter and charge the same against each tract of land so paid on, in a book to be kept by him for that purpose, showing the amount paid, date of payment, and to whom paid. Whenever any of said tracts of land are sold, the purchaser thereof, in addition to the purchase price therefor, shall pay all of such accrued assessments so paid, together with interest thereon, from the date of payment at the rate of six percent per annum, such accrued assessments and interest thereon to be included in the total purchase price to be paid by said purchaser; except that this section shall not apply to such assessments which have been paid by the lessees of any such tracts of land theretofore leased from the state as provided in section 37-43-117.L. 09: p. 430, § 5. C.L. § 2030. CSA: C. 90, § 492. CRS 53: § 149-3-15. C.R.S. 1963: § 150-3-15.