Abstract: Eight forest tree species,namely,Pinus bungeana Zucc.,Pinus tabulaeformis Carr.,Salix babylonica L.,Populus tomentosa Carr.,Eucommia ulmoides Oliv.,Paulownia elongata S.Y.Hu,Sophora japonica L.,and Ulmus pumila L.,representable conifers,diffuse-porous and ring-porous hardwoods respectively,were studied based on the samples collected periodically from trunk and crown branch of every tree during 1979 and 1980.Rhythm of periodical differentiation in cambial zone and sychronization with the characteristics of tissues and cells developed within a growth ring both in phloem and xylem were founded on facts of developmental anatomy.The trend of quantity and rate of tissue elements produced at different periods,the relations to phenology and environmental effects were analysed.All the studied typical ring-porous trees showed quite a different pattern of development as compared with others.Among the differences attracted attention,they resumed cambial activity in spring at the lower portion of trunk apparently much preceded the crown branch.Some problems on cambial study and its role in the control of shoot growth,and growth coordination in trees were discussed briefly.Besides,this general comparative study offers some indications that investigation on cambium,the formation of phloem and xylem,and relationship to tree growth should be integrated.The trend of this integration is worthy to be developed, because it will not only get a better understanding of cambium,but also help to forest practice for better production of wood and a part of bark.