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The effect of soluble starch (acid-modified starch) on taste intensity was investigated in human subjects. Different concentrations of sucrose (Suc), six sweeteners, NaCl, quinine–HCl (QHCl) and citric acid (Cit) were dissolved in either distilled water (DW; standard) or starch solution (test solution). The solutions were presented to naive subjects and each subject was requested to taste and compare the sweetness intensity between the standard and test solutions based on a scale ranging from +3 (enhanced) to –3 (inhibited). A greater sweetness intensity occurred with Suc at different concentration (0.1–1.0 M) dissolved in soluble starch (0.125% to 4.0%) than with Suc in DW. Similarly, five other different products of soluble starch at 0.25 and 4.0% resulted in enhancement of sweetness for 0.3 and 1.0 M Suc. With the sole exception of the taste of 0.3 M Suc, sweet enhancement did not occur with 0.43 M fructose, 0.82 M glucose, 0.82 M sorbitol, 0.0037 M aspartame, 0.0042 M saccharin-Na or 0.016 M cyclamate. Neither the saltiness of NaCl (0.01–0.3 M), the bitterness of QHCl (0.00003– 0.001 M) nor the sourness of Cit (0.0003–0.01 M) were affected by the soluble starch. These results suggest that the taste enhancing effects of soluble starch on Suc sweetness might depend not only on the taste transduction mechanism, but also on the molecular interaction between Suc and soluble starch.

In this study about the weeds on arable lahd in Japan, the following five groups were suggested from their present geographical range, though it must be admitted that we cannot show their origin exactly. The historical consideration has also been given in this paper. 1) The recently naturalized plants have been introduced in recent year. 2) The old naturalized plants were introduced from Europe or Eurasia through China in the early stage of history. 3) Cosmopolitan. 4) The prehistoric naturalized plants were introduced from Central and South China in ancient times. 5) Native species. 1) The recently naturalized weeds on upland field : 27 species were originated from Europe, and some of the most important are as follows; Senecio vulgaris, Veronica arvensis, Cerastium visosum, Rumex Acetosella, Festuca Myuros, etc.; 5 from Eurasia, Veronica persica, etc.; 9 from Nouth America, Erigeron annuus, E. canadensis, Euphorbia supina, Oxalis Martiana, etc.; 6 from New Tropical regions or South America, Oenothera odorata, Amaranthus retroflexus, etc. 2) The old naturarized weeds: 8 species were originated from Europe. Sonchus brachyotis, Vicia sepium, V. tetrasperma, Stellaria neglecta. Polygonum nodosum, P. Persicaria, Poa annua and Polygonum lapathifolium. All these species are upland field weeds, except the latter one which is paddy field weeds. 25 species were originated from Eurasia, among them Galium spurium, Elsholtzia patrini, Lamium amplexicaule, Capsella Bursa-pastoris, Chenopodium album, etc., are in upland field, whereas the following 13 species are in paddy field, Elatine triandra, Cardamine flexuosa, Ranunculus sceleratus and the others. 3) The species of old world origin or Cosmopolitan; 27 species on upland are Stellaria aquatica, Bulbosylis barbata, Digitaris adscendens, Equisetum arvense, 0xalis corniculata, Portulaca oleracea, Amaranthus ascendens, Polygonum aviculare, etc.: 26 are found in paddy field, among them there are Bidens tripartita, MyrioPhyllum verticillatum, Nasturium palustre, Eleocharis acicularis, Hydrocharis asistica, Ceratophyllum demersum, Najas marina, etc. 4) The prehistoric naturalized species: They are originated from South eastern Asia and especially interesting because these weeds are attendant on rice plants. Among them, Eclipta alba, Dopatorium junceum, Lindernia angustifolia, L. Pyxidaria, Limnophila sesseliflora, Ludwigia prostriat, Rotala indica, Monochoria vaginalis, Eriocaulon sieboltianum, Cyperus diffomis, C. Iria, Fimbristylis miliacea, Echinochloa crus-galli var. oryzicola. etc. are most important. 5) The Japanese native species; there are endemic species and the mutual common species in Japan, Korea, China, or Siberia, etc. The former contains only two species; Pleioblastus spp. and Sagittaria Aginashi. The latter would be perhaps the native species in those days when Japanese archipelago was detached from the continent (the last part of Diluvial epoch or the early years of the Allucual epoch) The native species which can be seen in Eastern as well as Northeastern Asiatic continent are amounted about 130 species on upland field and about 90 on paddy field. The most species, however, are slightly harmuful weeds, i.e., they are grown on the bordering foot-path or in the edge of irrigation ditches. A few species are noxious. As mentioned above, most of the troublesome weeds in Japan were found among the foreign species

(1) The mode of distribution was examined based on the dispersion diagram (unit area 6×6, 3×3 sq. cm.). It was calculated by means of X2-test for the deviation from the POISSON distribution, POISSON type by BLACKMAN, double POISSON type by THOMAS and POLYA-EGGENBERGER type on the important species in weed communities on various crop fields and fallow fields. (2) It is generally recognized that the distribution types of species such as Polygonium Blumei, Digitaria adsedens, Cyperus Iria, Dopatorium junceum, Rotala indica, etc. which propagate by scattering seeds were fitted satisfactorily to POISSON series of random distribution, when the, goodness of fit by means of X2-test was tested, though there were two types, one was more suitable to BLACKMAN'S value and the other to THOMAS' value, when the, value of actual density (D) to BLACKMAN'S type (m) or THOMAS type m(1+λ) were compared respectively (Table l). But the distribution of weed species including Aneilema Keisak, Eleocharis acicularis, Juncellus serotinus, which propagate by such an organ ds root, solon, rhizome, was fitted to THOMAS' type and PE type of contagious distribution. (3) It was recognized a linear relation as the fitness of MOTOMURA'S law of logarithmic series, namely, the log. number of individuals-rank and the log. weight-rank of species relation were shown on some growth stages on the weed communities in fallow field. Then before and after of these stages it was indicated L-type or S-type (Fig. 1). It is also shown a linear relation from the community including rice crop plants and weeds (Fig. 2). Such a linear relation seems to indicate a kind of the temporary stability of interspefic competition.

1) Tests were made on (1) germination of barnyard grass seed, (2) tolerance of the young barnyard plants to submergence in water, and (3) the effect of flooding on the top and root growths of the rice plants and its yield. 2) Rice plant were planted on June 28th, 1950 in concrete boxes, having glass wall on one side. On July 5th all weeds were removed and seeds and seedlings of the barnyard grass were planted between the rice plants. The amounts of water of respective boxes were adjusted to soil saturation and 5, 10, 15 and 20 cm. deep. Their conditions were held for 15 and 30 day periods and then all plots were flooded 5 cm. deep to mature. 3) With the increase in the depth of water the germination of the seeds of barnyard grass decreased. But in the laboratory, Tainubie (Echinochloa Crus-galli BEAUV. var. oryzicola OHWI) showed a considerable germination even at 15∼20 cm depth of water. 4) Many weeds that grew in paddy fields showed more or less tolerance to submergence, in water even when entirely submerged. Most of barnyard grass died after having been entirely submerged in water of 20 cm. for 15∼30 days. In the case of 15 cm. depth, a few plants survived. Barnyard grass developed the best on the saturated soil and next best in soil submerged for 5 cm. 5) Rice plants also showed considerable tolerance to water. The yield from 10∼20 cm. depth was equal to that of 5 cm. depth. As to the number of tillers, the treatment of 20 cm. of water held for 15∼30 days was momentarily poorer than the 5 cm. and rice plants tended to lodge. 6) The growth of rice plants on the saturated soil was inhibited on account of much weed growth and therefore its yield was small.

l. The crab grass occurs as a dominant weed on both thes weed potato and soybean fields. Both crops are susceptible to 2, 4-D, but the crab grass is resistant to this herbicide. Post-emergence spray of 2, 4-D on these crops, therefore, cannot be expected as a practical means. 2. During 1948 to 1951, field tests of weed control with 2, 4-D were made: (a) pre-planting treatment, (b) pre-emergence treatment and (c) between-row spray. 3. 75 to 150 grams of 2, 4-D per l0 ares were sprayed on the ridged beds, and after a rain, the sweet potato slips were planted. All of the slips took root and the growth of the crop was not retarded. Its yield equalled that of the weeded plot, with the weeds reduced to 1/1O ∼1/3 of those in the untreated plot. 4. When sweet potato slips were planted immediately after 2, 4-D was applied, the crop was severely injured, particularly in the drought year. But, those roots that were moistened and dusted with active carbon were delivered to some extent from the 2, 4-D injury. 5. The pre-emergence spray of 150 grams of 2, 4-D per 10 ares was considerably effective for the weed without decreasing the yield of soybean. A spray of more than 150 grams was injurious for the growth of the soybean. Seeds coated with active carbon prior to sowing was not injured even by the spray of 450 grams of 2, 4-D. This was attlibuted to the protecting action of the active carbon. 6. The soil treatment with 2, 4-D between the rows, after tillage, cares being taken in avoiding splash of the herbicide on foliages of the crop, was more effective on the annual weeds than pre-emergence tratment. The soybean plant was not injured by the applications of l00 grams of 2, 4-D per l0 ares on dry soil and 200 grams on moist soil. The yield decreased as the amount of 2, 4-D given increased.