In order to reexamine the cross-inoculation groups and to know the behavior of each type of rhizobial trains (classified in the previous papers) to legumes, cross-inoculation studies were performed. According to the results obtained, the so-called cross-inoculation groups may be admitted, though not without considerable irregularities. Such irregularities are particularly marked around bean (Phaseolus vulgaris) and cowpea (Vigna sinensis). It is also to be noticed that the relation between Medicago denticulata and Melilotus alba (or Medicago sativa) is hardly recognized to be reciprocal. Among the legumes used, Albizzia, Calopogonium, Centrosema, Crotalaria, Desmodium, Mucuna, and Tephrosia are all included in the cowpea group. Indigofera (and certainly Styphnolobium) will also come into the same group. Vicia nipponica may belong to the pea group. The results on Sesbania and Astragalus (sinicus) agree with the proposition of some investigators that each of them constitutes an independent group, respectively. From the reason that very few of rhizobial strains from already known inoculation groups are able to from nodules on Mimosa and Leucaena, and the cross-inoculation between the two is reciprocal, one new group, in which Mimosa and Leucaena are included may be proposed, though the relation between Mimosa and Dalea (or Sesbania) remains to be studied. Sophora seems to be a separate group. That the strains from one group or even from one plant are not always similar in the nodule production kinship is clearly proved in the subgroups of rhizobia from alfalfa, soybean, cowpea and Sesbania. But further careful studies will be necessary in this respect, because there are not few cases that the strains grouped in the same position do not always behave in like manuer. Finally, it is to be added that some plants (or strains of rhizobia) are able to symbiose with wide range of strains (or plants), while others do so only with very limited range of them.

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In order to obtain further knowledge on the irregularities existing between soybean-and cowea-group, inoculation experiments, in which soybean plants were inoculated with strains of rhizobia isolated from various legumes belonging to cowpea group, were made. The type B of cowpea bacteria is added to the strains which infect soybean. That such various types as A, B, D and F of cowpea bacteria infect soybean shows the intimate relation between soybean and cowpea-group, but the proposal that both groups may be brought under one group is hardly acceped, because there are not few strains which are unable to infect soybean, and moreover, the type A of cowpea bacteria which is usually found in cowpea nodules is hardly isolated from soybean in the field. Concerning the finding that there are strains which are able to infect soybean in the type B of cowpea bacteria, it is considered that the strains of soybean bacteria (type A) may be isolated from cowpea nodule, because as described in the previous paper, some plants of cowpea group are easily infected with soybean bacteria (type A). And since it is proved that the infective power of rhizobia is not easily altered by first passage through plant other than their original hosts, the adoption of such strain as type B of cowpea bacteria which corresponds to type A of soybean organisms will make the relation between soybean-and cowpea-group be reciprocal. Consequently, it is easy to understand that one of the factors determining whether the relation between the two groups is reciprocal or not is the strains used as cowpea bacteria. When such strains as types A, B, D, and F which infect soybean as well as cowpea are used, the reciprocal relation will undoubtedly be established. The kinds of plants included in cowpea group are so diverse and each of them seems, more or less, differ in the range of strains of rhizobia with which they symbiose, respectively. The relation of soybean and the plants of cowpea group to the range of rhizobia is the other important factor.

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Clays portions (0.2μ>) separated from both a surface layer and a subsoil of a calcareous paddy field have been investigated. The results of the investigations by chemical analyses and electron-micrographs were reported in a previous article. In the present paper, the same clays are studied through dehydration methods, differ(e)ntial thermal analyses, and x-ray diffraction methods The dehydration curves obtained are like to that of beidellite although in the portion of high temperature over 400℃ the weight loss is higher to some extent than beidellite and the general tendency of the curve is more or less parallel to illite. The moles of water loss above 400℃ is calculated on the basis of per unit cell. The value which corresponds to the OH in the lattice is 2.5 moles of water per unit cell and this supports the conclusion from chemical analyses in the previous paper that there may be five (OH) group in one lattice unit. The differential thermal curves of both clays from the surface layer and the subsoil show two endothermic peaks at 150℃ and 530℃ and exothermic peak at 850℃. These curves are like to the curves of nontronite-type clays. However, the X-ray patterns are nearly equal to that of Fe-montmorillonite. From these investigations the authors conclude that the clays finer than 0.2μ are nontronites of beidellitic, some illitic, and Fe-montmorillonite-type. The conditions forming these clays arese attributed by the authors to a high pH, to a high saturation with bases especially to Ca, to an impermeable character of the profile, and to a high Fe^<++> ion supply in a paddy field in cropping periods.

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1. The soil profile is formed from the weathering product of granodiorite covered by the mixture of hornblende gabbro and ash of dacite, and also by that of hornblende gabbro, ash of dacite and ash of pyroxene andesite. 2. The occurrence of minerals of montmorillonite group, hydrated-halloysite and kaolinite in the soil is clearly shown by X-ray powder photographs. 3. The cation-exchange capacities are about 50m.e. except in the fraction of No. 9,0.5〜1.0μ, but the molecular SiO_2/Al_2O_3 ratios are about 2.5 in those fractions, which seem to contain much of the minerals of montmorillonite group from the results of X-ray powder photographs. These facts indicate that the mineral of montmorillonite group may be beidellite. 4. The differential thermal curves clearly show the occurrence of beidellite, hydrated-halloysite and kaolinite. A small amount of montmorillonite may be contained. 5. The translucent and the opaque minerals, which appear on the electron micrographs, seem to be beidellite and hydrated-halloysite or kaolinite respectively. 6. The occurrence of beidellite, hydrated-halloysite and kaolinite in the soil is proved by these experiments. A small amount of montmorillonite may be contained in some fractions. 7. It is distinct that in the profile kaolinite is formed in relation to the granodiorite, and beidellite and hydrated-halloysite, to the hornblende gabbro and the two kinds of volcanic ash. Hydrated-halloysite is formed from volcanic ash in general in the soils in Japan, and the minerals of montmorillonite group seem to be formed at the environment rich in bases. From these facts, beidellite seems to be formed in relation to the hornblende gabbro, and hydrated-halloysite, to the two kinds of volcanic ash. Lastly, it must be added that some of the clay minerals, have been called beidellite, are shown by GRIM and others to be a mixture in which illite is an important component, or a mixed layer aggregate of montmorillonite and illite.

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In 1942,M. B. RUSSELL proposed an apparatus for measuring low-suction pore distribution in soils, however, it has some disadvantages in operation, especially when used for loose soils having much large pores. The authors gave some modifcations to this apparatus as shown in Fig. 1. Through these simple modifications the disadvantages have been overcome and a lighter liquid such as CCl_4 (for cheaper one) are used satisfactory to obtain as high as 150 cm height of water column. Furthermore, it is clarified that RUSSELL's method to measure a suction force from the center of soil column is incorrect and it must be measured from the upper most surface of soil column.

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It is observed that some of the salty paddy fields in coastal areas form very acid soils after drainage. The authors made the experiments in order to ascertain whether such acid marine soils exist or not in coastal areas in Japan. The soils investigated in this study were taken from salty paddy fields which are distributed along the seacoast of Okayama, Hiroshima, Yamaguchi, Tokushima, Kochi and Ehime Prefectures. Soil reactions and soluble salts were determined after the incubation of soils during three weeks at 30℃ under the condition of the moisture content of field capacity. The results obtained may be summarized as follows : (1) The reaction of soils lies within the range of pH from 1.3 to 6.6. Most of these samples show strong acidities, ranging from pH 1.3 to 5.0. (2) Soluble salt contents of these soils are very high, ranging from 0.4 to 1.9 percent. It is found that sulphates are dominant in the soluble salts and come to be increased with the increase of total salts. A relatively good correlation is found between pH value and sulphate content. (3) It may be assumed that the strong acidities found in incubated soils were brought about by the oxidation of sulphides which had been formed in an anaerobic condition. The damage of rice plant in these paddy field is considered to be caused by the accumulation of relatively large amounts of sulphides, especially soluble sulphides and its oxidized acidic compounds. Concerning the reclamation of the depressed land, it is a noteworthy fact that a good many of soils from coastal areas become extremely acidic after drainage.

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By the previous report, it was understood that the effect of heating soils at increasing temperatures, from 300℃ to 600℃, influenced upon the dye absorption in two ways, increasing and decreasing. The absorption was increased with the soil of volcanic ash origin and of a lower ratio of SiO_2 to Al_2O_3,but it was decreased with the acid mineral soil of a higher ratio of SiO_2 to Al_2O_3. This time, the effect of removing constituents, dissolved by the mixture of oxalic acid and ammonium oxalate, from the soil to the absorption was examined, resulting in the same way with the above soils as the absorption being decreased. Compared to the previous result, the constituents, dissolved by the mixture, seemed to cause the absorption to be increased with an increase of heating temperature remarkably with the soil of a lower ratio of SiO_2 to Al_2O_3 and of volcanic ash origin.

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Content and quantity of some constituents of the middle of tobacco plants with different phosphate levels at succesive periods after topping were studied. The results were shown in Table 1 and 2. The middle leaves of tobacco plants with low phosphate level had higher content in pectin, crude cellulose, lignin, malic acid and total resin and lower in protein, nicotin, oxalic acid, wax and gum compared with those with high phosphate level. There was no clear difference in tannin and citric acid content independent of phosphate level. After topping, content in pectin and malic acid of tobacco leaves decreased and nicotin, tannin, wax and gum increased to each maximum with subsequent decrease, but pectin, crude cellulose, lignin, oxalic acid and total resin increased to the end. Considering the delayed changes in content of cell wall materials, nitrogenous compounds and tannin of the middle leaves of tobacco plants with high phosphate level, it seems to be reasonable to conclude that the time of maturity of tobacco leaves with high phosphate level is later than that with low phosphate level.

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