The
legislature shall provide such revenue as may be needful, by levying a tax by
valuation, so that every person or corporation shall pay a tax in proportion to the
value of his, her, or its property, except as in this article hereinafter otherwise
provided. The legislature may also impose a license tax, both upon natural persons
and upon corporations, other than municipal, doing business in this state; also a per
capita tax: provided, the legislature may exempt a limited amount of improvements
upon land from taxation.