Through some additional searching, I discovered that the ability to have text-only buttons was removed in version 29, which means my upgrade must have been from 28. I installed [https://addons.mozilla.org/en-US/firefox/addon/classicthemerestorer/ Classic Theme Restorer] to attempt to get this capability back, but it completely messed up my toolbar. Plus, I don't like the idea of having to install a plug-in with tons of options and questionable future compatibility just to get back a simple feature that has long been a part of the application. So, I have reverted to Firefox 28 while I look for another browser. Combined with long-standing performance issues, this was really the last straw for me. Believe it or not, text on buttons dramatically helps workflow, as is supported by significant UI research, and making them text-only saves space. I can't imagine why this capability was eliminated.