The state treasurer is authorized by this article [6-12-1, 6-12-2 N.M. Stat. Ann.] in order to provide for the prompt payment of interest on the bonded indebtedness of the state, to borrow money upon the best terms possible, but at a rate of interest not to exceed six percent, and for the shortest practicable time, in quantity sufficient to pay any interest as it accrues, whenever the money in the state treasury, applicable to such payment is insufficient to meet interest coupons as they mature, unless there should be in any one or more of the funds in which are placed the proceeds of the administration of public lands donated to the territory or state of New Mexico by congress, money which is not needed for immediate use for the purposes for which such lands were donated and which is to be invested in accordance with the requirements of the acts of congress and of the constitution, or funds in the permanent school fund, in which case the state treasurer may invest so much of such fund, or funds, as may be necessary for the purpose of meeting the interest-bearing obligations, in an interest-bearing obligation to be executed by him, the interest thereon to run until both principal and interest can be paid back to the fund or funds from which it may have been borrowed.