38. After such inquiry as he may think necessary, the Collector shall decide the amount of compensation payable and such decision shall be subject to an appeal to the Commissioner of the Division: Provided that such appeal be presented to the commissioner, or to the Collector for transmission to the Commissioner, within thirty days of the decision appealed against. If no such appeal be preferred, the decision of the Collector or, if such appeal be preferred, the decision of the Commissioner shall be final and conclusive.