æt ðə smɪθsˈoʊniən, hiː wʌz fˈɜːst dᵻɹˈɛktɚɹ ʌvðə dᵻpˈɑːɹtmənt ʌv bˈɑːtəni ænd ðˈɛn ɐ dᵻɹˈɛktɚɹ ʌvðə nˈæʃənəl mjuːzˈiəm ʌv nˈætʃɚɹəl hˈɪstɚɹi, ænd tʃˈɛɹd sˈɛvɹəl ɪmpˈoːɹtənt saɪəntˈɪfɪk səsˈaɪəɾiz, sˈʌtʃ ɐz ðɪ ɐmˈɛɹɪkən səsˈaɪəɾi ʌv plˈænt tæksˈɑːnəmˌɪsts.
At the Smithsonian, he was first director of the Department of Botany and then a director of the National Museum of Natural History, and chaired several important scientific societies, such as the American Society of Plant Taxonomists.