Hitherto, it is commonly said in this country that Sugi (Cryptomeria japonica) may be subdivided into two subspecies or two types, namely Omote-sugi (Pacific type) and Urasugi (Japanese sea type). The former has roundheaded crown and straight leaves which are attached to twigs at obtuse angle. Its growth is rapid in young stage, but soon becomes slow, and is often injured by snow in northern district. The latter has conical crown and curved leaves which are attached to twigs at acute angle. Its growth is slow in young stage, but later becomes vigorous and continues without being injured by snow.
In our survey of some natural forests of Sugi in the Chuhgoku Mts. in western Honshuh in the fall of 1956, we were impressed that the theory of subdivision above mentioned of Sugi is not well-founded sufficiently So we looked through literatures concerned, and concluded as follows.
1. It seems to us that differences in the growth, which were observed formerly by some investigators, should not be due to "types" but to "varieties".
2 . Crown type of Sugi were observed hitherto with no consideration of its site and physiological age, and results obtained till now did not agreeed completely. From these results we should not subdivide Sugi into two types.
3. We think leaf type is useful to recognize genotype of Sugi, Among characters belonging to leaf type, angle of leaves attaching to twigs is useful specially, because it can be easily measured and its data obtained till now is not few. From those data and our recent observations, it seems to us that angles of leaves increase gradually from north to south following the situation of the natural forests, and also among seedlings in nurseries, from seeds gathered from many places allover in this country. This tendency of angle increasing is continuous and fairly irregular, so a distinct line dividing this country into two parts should not be given corresponding to the types of Sugi. There may be certain hereditary factor in Sugi which was influenced gradually in different degree following the direction from north to south in this country.