“Most of us think of Darwin at work on The Beagle, taking inspiration for his theory of evolution from his travels in the Galapagos.” So opens the Profile Books’ introduction to Dr. Ken Thompson’s recently published “Darwin’s Wonderful Plants.” I know I certainly did. That is, of course, until I made a visit to Down House this past summer and saw for myself his remarkable greenhouse and gardens, where he spent the decades following the return from his famous voyage cultivating and experimenting upon plants – particularly carnivorous and climbing ones.