For example, www.schwab.com says as follows, but I hate to depend on something on the web, I'd just like to know  how they arrive at the position:

Long-term capital-gain property

You can usually deduct the full fair market value of appreciated long-term assets you've held for more than one year, such as stocks, bonds or mutual funds. In addition, if you donate stocks or other investments, you pay no capital gains tax.

Donating investments—especially highly appreciated securities—instead of cash can be a very effective and tax-efficient way to support a charity. Generally, if your assets have appreciated in value, it’s best not to sell securities to generate the cash you need for a donation. Contributing the securities directly to the charity increases the amount of your gift as well as your deduction.