ɪn nˈaɪntiːnhˈʌndɹɪd twˈɛnti ˈeɪt, hiː bɪkˌeɪm ɐ stˈæf mˈɛmbɚɹ ʌvðə nˈuː jˈɔːɹk bətˈænɪkəl ɡˈɑːɹdən ænd mˌeɪd hɪz fˈɜːst tɹˈɑːpɪkəl tɹˈɪps tə kəlˈʌmbiə, pɚɹˈuː, ænd bɹɐzˈɪl fɹʌm nˈaɪntiːnhˈʌndɹɪd twˈɛnti sˈɪks tə nˈaɪntiːnhˈʌndɹɪd twˈɛnti nˈaɪn.
In 1928, he became a staff member of the New York Botanical Garden and made his first tropical trips to Colombia, Peru, and Brazil from 1926 to 1929.