What is the single best herbal medicine reference book for a trip to Africa?

I will be joining a development istance project in Malawi, Africa, very soon. They recommend volunteers bring seeds for their own use, so of course I'm taking some of my favorite medical and culinary herbs... but I would like to be able to look up and perhaps utilize native species as well. Internet access is extremely limited, as is packing space. Does anyone have a recommendation for an extremely complete text I might take along? It needs to be a single book, not a hardbound encyclopedia set, and it needs to cover as many herbs as possible, especially African ones. I always liked the layout of the Herbal Vade Me, but it doesn't cover doses, identification, or all that many African species. Is there anything you know that fits the bill?