I've been back at Grinnell for about a month now, and so far my semester's off to a great start! Very busy, but not busy enough to prevent me from finishing up my data analysis.
It looks like Echinacea purpurea's breeding system is similar to Echinacea angustifolia's. Styles that receive compatible pollen shrivel up within a few days, whereas styles that don't persist longer, often for more than a week. In addition, E. purpurea is self-incompatible. (This means that an individual plant can't pollinate itself, it needs pollen from another plant of the same species.)
To complicate things a little:
Not all of the flower heads I was studying had finished flowering by the time I left Minnesota, so I do not have much data on the top several rows of styles on many of them. Since styles in higher-up rows persist somewhat shorter than in lower rows, I cannot be sure that the trends I saw in my data hold for the top rows of all flower heads.
Also, some of the statistical tests I ran showed that style persistence in the self-pollination treatment differs significantly from the control treatment, while others do not. I'm not sure why that would be.
If anyone has any suggestions for improvement or other things I could look at with this data, please let me know!
And I posted much of my data analysis on H. helianthoides already, but here are the "final" versions. (But, again, I'm open to suggestions for further improvement!)