1. Comparative anatomy of the leaf-bearing Cactaceae, VI. The xylem of Pereskia sacharosa and Pereskia aculeata;Bailey;Journal of the Arnold Arboretum,1962
2. Comparative anatomy of the leaf-bearing Cactaceae, VII. The xylem of pereskias from Peru and Bolivia;Bailey;Journal of the Arnold Arboretum,1963a
3. Comparative anatomy of the leaf-bearing Cactaceae, VIII. The xylem of pereskias from southern Mexico and Central America;Bailey;Journal of the Arnold Arboretum,1963b
4. Über die systematischen Gliederungen der Cactaceae;Barthlott;Beiträge zur Biologie der Pflanzen,1988
5. Zonation in the shoot apices of Trichocereus spachianus and Opuntia cvlindrica;Boke;American Journal of Botany,1941