Abstract
The structural features of non-photosynthetic organs in some tree species were analysed in relation to the basic theory of quantitative geomorphology of channel networks in drainage basins. Although Horton's law in channel networks was found to satisfy the branch networks of trees, branch networks resulting of many forms of life were different from those of geomorphology in the distribution of parts. The following conclusions were deduced from the resultant features of branch networks in comparison with the bifurcation ratio of channel networks. 1) The bifurcation ratio of networks of branches in Horton's law showed a considerable variation from 3.0 to 8.0,the range being larger in trees than in wateraheds. 2) One species of a young Quercus tree had some stable value of the bifurcation ratio in the different conditions of environment. 3) The values of the bifurcation ratio of trees were divided into several groups by the life form of the tree species. 4) The determination as to which bifurcation ratio of the four fell was interpreted as the differences of the size of space of the first order branch which was the small branch with leaves at the point of the bough, and the differences of shade tolerance of leaves by which the small branches make use of the limited space for the branches.
