The state board of agriculture shall from time to time, in their discretion as they may deem necessary to protect the best interests of the state, cause the lands under their care to be examined and their value and condition ascertained. To this end they may appoint 1 or more agents who shall make careful, personal examination of the lands which they are appointed to examine and report fully as to their character, value and condition at the time of such examination and in case any of said lands have been trespassed upon and their value deteriorated thereby, the agent examining such lands shall carefully estimate and report the amount and character of timber probably cut and removed, the date of the cutting and if possible, by whom or for whom the cutting was done. Upon receiving such reports of examination, the state board of agriculture shall consider them and if in the opinion of the board the best interests of the state would be promoted by changing the price or terms of sale of any or of all the lands concerned, the said board may alter by reducing or advancing the price per acre or the conditions of payment: Provided, That not less than 25 per cent of the purchase money shall be paid at the time of purchase. And when [the] price and terms are so fixed the said board shall fix the time when the change, if any be made will take effect, and cause the same to be published.