How a herbarium helped to lay the foundations of evolutionary thinking.

, was also a rig-orous researcher who recorded patterns of vari-ation within and between plant populations andwas motivated to understand the nature ofspecies: the big question of natural history as he saw it. The focus of Henslow’s research is evident in his herbarium at Cambridge, whichholds 3,654 sheets of British plants that hebegan assembling in 1821. These sheets repre-sent 89% of the species that Henslowrecognized in his 1829