Marc uses "Botany in a Day", by Thomas Elpel as his guide. You can probably find a copy at your local library. I did.
Marc's website, Botany Everyday, is full of content and contributions from people all over the world. It's a place you can learn a lot and spend useful time in your quest to gain knowledge about nature.
I first met Marc at a Wild Fermentation workshop at the Hostel in the Forest. I learned about mead making, sauerkraut crafting and lots of other ways to ferment. It opened up a whole world for me. Marc and Mycol Stevens are giving another workshop at the Hostel in the Forest the weekend of May 4th. Click here for more info.