hɪz kˌɑːntɹɪbjˈuːʃənz tə ðə fˈiːld ɪŋklˈuːd ɐ mˌɛkɐnˈɪstɪk tɹˈiːtmənt ʌv dˈɪfɹənt mˈoʊdz ʌv sˈɛlfpˌɑːlᵻnˈeɪʃən ɪn hˌɜːmɐfɹədˈɪɾɪk plˈænts, ɐ dʒɪnˈɛɾɪkli dᵻfˈaɪnd kəntˈɪnjuːəm ʌv plˈænt dʒˈɛndɚ, ˈɜːli dɪvˈɛləpmənt ʌv θˈiəɹi ʌvðɪ ˌɛvəlˈuːʃən ʌv sˈɛpɹət sˈɛksᵻz ɪn plˈænts, ænd wɪð sˈiː.dʒˈeɪ. wˈɛb, ɐ tʃˈælɪndʒ tə kənvˈɛnʃənəl vjˈuːz ʌvðɪ ˌɛvəlˈuːʃən ʌv hˈɛɾɚɹˌoʊstili.
His contributions to the field include a mechanistic treatment of different modes of self-pollination in hermaphroditic plants, a genetically defined continuum of plant gender, early development of theory of the evolution of separate sexes in plants, and with C.J. Webb, a challenge to conventional views of the evolution of heterostyly.