...I can't think of a better way to start than by looking up this book about the ethnobotanist Richard Schultes, and his years of Amazon exploration. The Lost Amazon is by Wade Davis. An amazing story and remarkable photographs.
Also, I hope you can find some of the volumes to do with the seminal work in the area by the botanical artist, Margaret Mee. (She also plays a small part in The Whirling Girl -- off stage, of course.)