Tobacco seedlings are transplanted between wheat ridges in early spring when there are still dangers of low temperature and late frost. It is necessary, therefore, to study the microclimate of the field accurately. For this purpose, the writers investigated temperatures of air, soil and seedlings (surface and back of the leaf as well as growing point) and rate of evaporation in the fields where direction of ridges and position of the seedlings between ridges are variously different (Fig. 1).
The results are summarized as follows:
1. Air and soil temperatures were measured by thermister (Fig. 2). In the night time air temperature on the naked field was lower than other fields. In the west side of south-north ridges and in the north side of east-west ridges, the morning temperature at the height of 10-50cm above the ground was considerably low by the shade of wheat. For the same reason, low temperature was observed in the east side of south-north ridges and the north side of east-west ridges in the afternoon. At night, however, at the distance of 30-50cm above the ground-the distance of upper half of wheat height-the temperatures in wheat fields became lower than that in naked field forming a characteristic low temperature zone. At the lower half of wheat height, the temperature was higher than that in the naked field.
Similar trends were observed in the ground and underground temperatures, namely, in the west side of south-north ridges as well as in the north side of east-west ridges both temperatures were lower in the morning. In the afternoon, however, the temperatures in the opposite side of south-north ridges and those in the same side of east-west ridges became lower than those in the naked fields.
2. Temperatures at various positions of the seedlings were measured by means of thermo-couple. The results are shown in Tab. 1. In the day time, the temperature of leaf surface was 1-5° higher than that of the back of leaf as well as than that of the growing point. At night, however, the temperature of leaf surface became 1° lower than those of latter two. Every positions of the seedlings grown in the north side of east-west ridges showed the largest daily fluctuation of temperature. But in the seedlings grown in naked fields as well as in the seedlings grown in the north side of east-west ridges where they are shaded by wheat, the fluctuation was small and daily lowest temperatures were lower than those in the other plots.
In the morning, regardless of the direction of ridges, the temperature of the seedlings rose a little higher than that of the air at the position of 5cm above the soil surface. The difference, however, was inconspicuous after 2 o'clock p.m. At night, air temperature became heigher than that of the leaf surface (Fig. 3).
3. The result of harmonic analysis showed the largest amplitude of temperature in the south side of east-west ridges as well as in the west side of south-north ridges (Tab. 2, 3).
In naked field, in the south side of east-west ridges as well as in the north side of east-west ridges the amplitude tends to increase in accordance to the lowering of measured position.
In the west side of south-north ridges as well as in the south side of east-west ridges, the phases of temperature were larger than those of observed in the east side of south-north ridges.
In the north side of east-west ridges and in the east side of the south-north ridges, however, the phases were larger than those observed in naked field.
The amplitude of temperature at leaf surface was larger than those in the other positions of the seedlings. This phenomenon was observed in every plots. The amplitude at leaf surface was compared among ridges of various directions by which in the south side of east-west ridges the amplitude was the largest and it was the smallest in the north side of same ridges. The phase of temperature at leaf surface was the largest than any other positions of the leaf and

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The potential-evaporation on the bare ground has been recorded at the observing field for agro-meteorology located at Kashiwa City, Chiba Prefecture by using a potential evapotranspirometer. (Fig. I) The following two features were obtained from analysis of these records.
One of them is a sine curve form which is caused by the formation and melting of the bar frost (ice columns) in the cold season (Fig, 5, Fig, 3), and the other is the variation of water movement which is affected by the temperature profile in the ground except in winter. (Fig. 2, Fig. 4) These facts are also proved by the records of ground water level. (Fig, 6) The records of the evapo-transpirometer are not of course to show in the natural ground, but it seems to bear from some resemblance them in mehanism of the water movement.

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農作業の参考とする気温の統計として, 平年値は最近10年間の平均値を毎年計算して用いることを提案し, 農業関係で平年作を求める時のように, 平年値の算出にあたつて最高と最低の年を除外するような処置は現在の段階では必要のないことを示した。また日較差は農作業の参考として重要な要素であるが, これについての統計は従来あまり行われていないので, 日較差ゐ統計の一試案を示した。

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Result of a comparative observation made in and out of an orchard is given, and the temperature fluctuation of the leaf-surface in response to that of its contact air layer is examined by the photographic record.

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The effects of solar radiation, temperature, humidity and wind on the transpiration rate of rice plant were studied with the following results:
1. The effect of temperature on the transpiration rate was the largest when the temperature was about 26°C. When the temperature increased above 26°C or decreased below it the transpiration rate decreased. Assuming the tranpiration rate to be 100 at 17°C, the transpiration rate was 270 at night and 200 at day time when the temperature was about 26°C.
2. Assuming the transpiration rate to be 100 at 170lux, the transpiration rate was about 230 at 4, 100lux and about 320 at 89, 000lux.
3. Regarding humidity, the transpiration rate was nearly proportional to the saturation deficit between the range 3 to 15mm.
4. Assuming the transpiration rate to be 100 with no wind, the transpiration rate became 300-500 at a wind velocity of 12 meters per second and it had almost linear increase with the wind velocity.
According to these results, it can be concluded that the effect of wind on the transpiration rate is not always so smaller than that of solar radiation, humidity or temperature as has been hitherto taken for.

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1. 12m/sec―5時間の風処理は水稲の節間伸長を可成り抑制するが, 出穂期頃においては上位節間程大きい影響を蒙むる。
2. 節間伸長抑制の害が最も著しく現われる時期は, 節間位によつて異り, 各節間の伸長速度の大きい時期の処理に見られる。但し水稲稈長は実際上上位節間程大きい比重を占めるので, 稈長への影響は上から第1及び第2節間の伸長抑制の害が強く現れる出穂後1～3日目頃の処理において認められる。
3. 穂首の抽出抑制は止葉の葉鞘長には関係なく, 第1節間の伸長抑制の動行と併行する。
4. 第1節間の伸長抑制は穂の抽出を妨げ或いは遅延せしめて, 開花及び受精を不良にし粃を増加して稔実障害の原因となる。

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