Button style inside collapsible

Button style inside collapsible

A button added programmatically inside a collapsible (which is, in turn, part of a collapsible set) doesn't style the way other buttons do.  I've tried defining the button all 3 ways (as an html input type='button' tag, as an html button tag, and as an a tag).  The same html code moved OUTSIDE the collapsible set looks the way I expect buttons to look.  Inside the collapsible set, they retain the default underlined blue hyperlink for the text.

(Please note that after I add the buttons programmatically, I perform an initialization on them via the button widget's .button() method.)