He reported on the Botany of the Mexican Boundary Survey (1859), that of the expedition upon the Colorado River under Lieutenant Joseph C. Ives (1861), and, in association with Asa Gray, the botanical collections of the Wilkes exploring expedition.
Han berettede fra Botany of the Mexican Boundary Survey (1859), fra ekspeditionen til floden Colorado under løjtnant Joseph C. Ives (1861), og sammen med Asa Gray om de botaniske indsamlinger fra Wilkes opdagelsesrejse.