Note that Carl suggests in his response to my question in the link above that the fontSize could be set as a primary option or per-axis option. I didn't see the latter in the API reference here: https://github.com/HumbleSoftware/Flotr2/wiki/API-reference
The fontSize option has no effect on the Axis labels, see https://groups.google.com/forum/?fromgroups=#!topic/flotr2/XK0cB6CuCLY
Note that Carl suggests in his response to my question in the link above that the fontSize could be set as a primary option or per-axis option. I didn't see the latter in the API reference here: https://github.com/HumbleSoftware/Flotr2/wiki/API-reference