Most of the appreciation in these assets can be attributed to inflation.
Inflation caused by unrestrained spending by the Federal Government.
The 17th amendment states:
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.
There is no income on the appreciation of a stock until it is sold.
Strictly speaking, that would be the 16th.
The 17th regards direct election of senators.
Blame spellcheck. ;-)