We highly recommend the Missouri Plants website (http://www.missouriplants.com/) for good pictues and information useful to identify plants native to Missouri. It has useful listings of plants by flower color and leaf arrangement. There is also a complete list of plants by scientific name. Two useful lists it lacks is a listing by plant family and one by leaf arrangement. Following are these lists. Clicking on a plant will take you to the plant in the Missouri Plants website. The listing by family is particularly useful for gardeners who can recognize some plant families. The families used here are those used in the website.
Leaf arrangement can also be a useful grouping. In the right column below, plants are grouped by alternate and opposite or whorled, then by family. For lists of ferns, grasses, sedges and rushes see the listings in the website.