1. : Gehölzvermehrung. Ulmer Verlag, Stuttgart 1978.
2. : An Atlas of Plant Structure, Vol. 2. Heinemann Educational Books, London 1973.
3. : Gymnosperms, Structurer and Evolution. University of Chicago Press, Chicago-Illinois 1935.
4. : Morphology of Gymnosperms. University of Chicago Press, Chicago-Illinois 1910.
5. : Handbook of Coniferae. London 1910.