Most of our archaeologists have regarded obscurely that the origin of ricecrop and the history of rice-breeding began on the swampy grounds at the margin of ponds or marshes. Accurately speaking, however, the localisation of wet rice field was not on morass-grounds under stagnant water, but clay-loam or loamy bog-beds under nearly stationary shallow water. Such consideration was corraborated from recent ecological experiments. On the other side, I deduced “dry-land rice crop” by means of the shifting cultivation (Brandwirtschcft) was its origin. Morever, from bio-ecological viewpoint, I recognized that the dry-land cultivation was an agricultural type older than wet rice-farming (Sawah cultivation), especially in tropical and subtropical regions. Consequently, in view of the rudimentary technical stage of the primitive society, the condition of soil colloid and ecology of rice-plant, I concluded two courses on the origim of rice-farming regionally; one was dry-land crop, the other, wet rice field.
The distribution of the median 0ø, Mdø, of the fluvial deposits of main, rivers in Kanto plain is report_??_d in this article. The tractive fore of the current in moving bed-material, T, is given by T=WRI where R is hydraulic radius and I is gradient. But the hydraulic radius changes in very small scale comparing to the gradient, therefore the mean grain size of the deposits in this distric is mainly, deterniined by gradient.
By comparing yield per Tan of aquatic rice, wheat, common barley and naked barley in the towns and villages of Okayama prefecture with climatic factory. which have close relations with the yields, we deterniincd the climatic divisions. for crop culture. The date of the yield per Tan red for this research are of 367 towns and villages concerning the yields from 1920 to 1930, and the meteorological data were obtained from 38 meteorological observatories from 1916 to 1940. First of all, we researched what kind of climatic factors had most to do. with the yields of aquatic rice, wheat, common barley and naked barley. As its result, we found that the yield of aquat ie rice had a close relation with vegetable period; the number of days over 5°C in a year (D1), and amount of precipitation from Mey to October (P1), and on the other hand, wheat, common burley, nd naked barley had a close, relation with the n inber of days under 5°C in a year (D2) and amount of precipitation from April to June (P2) respectively. As the formula for the relation between the climatic factors and town and village yield per Tan, we obtained the results as shown in Tab. 2. Two times probable error of D calculated out by putting yield per Tan in Y are shown in the rightest column of Tab. 2 and these two tunes probable error w named as variability of climatic. The climatic divi;dons which were dividCd by these variability of climat are shown in Fig. 2. 3 and 4
The writer researched the reclamation process of the valley by the records written in feudal days and are preserved in the village offices. The records are named munatsukecho (cencus registers) and Kenchicho (terriers). 1). The lower part of the valley was colonized earlier, being the southern frontiers of the domain of local clan, but the middle and upper parts were reclaimed later on account of their narrowness and remoteness of the valley. The reclamations were active in three periods, namely 1670 (Kammon), 1690 (Genroku), and 1708 (Hoei). There were intervals of about twelve years in between, and the colonization progressed gradually from lower to upper valley. 2). Several years preceding the progress of the each reclamation, there entered many people from the other districts. For example the village of Aikawa was reclaimed at the beginning of Hoei, and several years before the time, a dozen houses moved thither, chiefly from Tosa. Namely the reclamation was achieved by means of these immigrated men and women. 3) Tomoura and Okuura, were located at the entry of the Kaifu river, and the former a fishing village and the latter commercial centre of the districts. They accepted many immigrants from adjacent districts, not to speak of Tosa. They, however, earned their living mainly by fishing and commerce, and did not need so much arable lands, therefore the reclamation did not progress so much as the upper parts of the river. 4). The nativeplaces of immigrants from Tosa were mostly Kannoura, None, and the western part of Muroto Peninsular.
At the region of the middle course of the River Watarase, gravel beds are classified as follows: (1) Godo Gravel Bed (oldest gravels) Their angularity and composition show that they are not the deposits of the River Watarase. (2) Upper terraces and the initial surface of Omama Fan They were formed before the deposition of Kanto Loam. (3) Lower terraces and the erosion surface Omama Fan It seems that they were formed during the deposition of Kanto Loam. (4) Flood plains of the River Watarase The writer researched the ratio of composition of gravel samples on each of terrace plains, from which he tried to interpret the mechanism of. formation of terrace plains. In this region the writer chose 22 stations for sampling. Samples were taken by roughly outlining a small area of about one meter in diameter. From this area 100 gravels were chosen at, random. Fig. 4 and Table 1 show the composition of the grayel samples collected. In Godo Gravel Bed, Pal ozoic rocks and Tertiary tuffs are common, white andesites only 11%. So the deposition of such gravels have not much relation to Akag. Volcano. Gravel beds on the initial surface of Omama Fan and upper terraces of Shiobara and Kambal, however, are mainly composed of andesites involved about 80%, which were chiefly derived from Akagi Volcano. It seems that those plains were formed by the increase of materials from Akagi Volcano, and the deposition of volcanic detritus from Akagi was most active during the formation of those upper terraces. On the lower terrace plains and the erosion surface of Omama Fan, percentages of andesites in gravel samples show 50_??_60% and that of the flood plains about 30%. Therefore, the writer's conclusion is that the deposition, of materials from Akagi Volcano decreased during the formation of lower terraces and such tendency of decrease has continued up to the present.