REPRINTED FROM TAXON 19(3): 468-480. JUNE 1970
Proceedings of the California Academy of Sciences Fourth Series Vol. XXV, No. 16, pp. 377-420, pls. 37-46 November 15, 1946
Reprinted without change of paging from Journal of the Arnold Arboretum, Vol. XXI 1940
Progress in Botany, Vol. 50_Springer-Verlag Berlin Heidelberg 1989