270.25  Special assessments or levies shall remain liens subject to payment.--Special assessments or special levies heretofore imposed by legislative authority, which are now a lien upon the lands, title to which is in the Board of Trustees of the Internal Improvement Trust Fund, shall continue as a lien subject to payment as provided for in s. 270.24; provided, however, that the provisions of this section shall not operate to extinguish or impair any obligation heretofore imposed upon said lands to pay special assessments or special taxes heretofore levied.