Plant identification resources?

Hello,

I recently went to my study sites for my master's thesis project to make measurements and observations about the plant community. A few of the agricultural streams I'm working in have a surprising diversity of plant species. Others, not so much (recently dredged). I was able to ID a good deal of the plants to the genus level, which is sufficient for my analysis. However, some of the plants have me stumped. Does anyone have a good on-line reference for aquatic plant species of the Midwest that they'd care to share? I found this one during a quick search;

Midwest Aquatic Plant Management Society


Thanks,

-Nate

nice guide thank you

I don't have anything for the midwest, but if you post photos, we can all try to help.