It is planned that a new citrus plantation of 90 ha is founded on the hilly highland where the elevation is 270 to 500 meters above the sea. Because this elevation is higher than any existing citrus producing district in Shizuoka Prefecture, the climatic adequacy for citrus culture of this area should be examined at first. For this purpose, the local climatic survey is carried out during the period from October 1969 to October 1970 and from the obtained data collected at 17 observing points in the area such indices are calculated as the yearly mean temperature, the average of the daily minimum temperature in the coldest month, the average of the daily maximam temperature in the warmest month, the accumulated effective temperature and so on. Moreover the wind velocity is also recorded at the observing points.
The obtained results are as follows:
(1) In the yearly mean temperature the difference of 1 to 2°is found between the data collected at the observing point of 300 meters above the sea and at the observing points of 400 to 480 meters above the sea. In the average of the daily maximum temperatures in the warmest month the difference of 2 to 3°C is found between the data of the same observing points. As the elevation increases, so the temperature lowers.
The average of the daily minimum temperatures in the coldest month lowers gradually as the elevation increases. On the other hand, though the elevation is low, the cold zone arises in such lowlying places as hollows or small valleys.
(2) The accumulated effective temperature in the citrus producing districts in Shizuoka Prefecture is distributed in the range of 2465 to 2655°C. It is not possible in the district where the accumulated effective temperature is bower than 2400°C to get a good citrus production.
(3) The accumulated effective temperature in this area amounts to 1793 to 2250°C. This value is too small comparing with the accumulated effective temperature in the existing main citrus producing districts. As the elevation increases, the accumulated effective temperature lowers.
(4) The occurrence frequency besed on return period of the minimum temperature in winter time is calculated at each observing point. From these results it comes to the conclusion that the minimum temperature below-6°C would not be observed, therefore, there is no dangerous area for Satsuma mandarin to freezing damage in this area.
(5) Wind is generally strong in this surveyed area because of the high elevation. Particularly strong wind is observed at the hill ridges and at the open areas with simple topography.
(6) The inadequate areas or the dangerous areas have been made clear by each indices which are calculated from the observed meteorological factors at 17 observing points. Further more, applying the synthetic jedgement on the obtained results, the authors Brow up the classification chart (Fig. 3) showing the inadequate area and the dangerous area in this surveyed area.

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Detailed Climatic Classification of Tohoku district is obtained by principal component analysis using climatic elements at 242 places.
Climatic elements are 11 as follow (numbers in parentheses are years of observation);
X₁: Monthly mean temperature at sea level, during May-Oct. (1931-60).
X₂: Monthry mean temperature at sea level, during Dec.-Mar. (1931-60).
X₃: Monthry mean diurnal range of temperature, during May-Oct. (1931-60).
X₄: Monthry mean diurnal range of temperature, during Dec.-Mar. (1931-60).
X₅: Total precipitation, during Apr.-June (1061-70).
X₆: Total precipitation, during July-Sep. (1966-70).
X₇: Monthly mean of daily minimum humidity, during Dec.-Mar. (1966-70).
X₈: Monthly mean of daily minimum humidity, during Apr.-June (1966-70).
X₉₁: Monthly mean of daily minimum humidity, during July-Sep. (1966-70).
X₁₀: Maximum depth of snow cover (1935-44).
X₁₁: Duration of continuous snow cover (1935-44).
Highly significant correlatiion is found between maximum depth of snow cover and duration of continuous snow cover, and is found between spring humidity and summer humidity. Also, high significant correlation is found between temperature of warm season and winter temperature, is found between spring precipitation and summer precipitation, and is found between winter humidity and duration of continuous snow cover (shown in Table. 1).
4 principal components are obtained in greater order (shown in Table. 2). But the contributory rate of the forth principal component is small and geographical distribution of scores are random, so this component is of no use for the classification.
The first principal component is put together chiefly in information of climatic elements of winter, snow cover, humidity and temperature. And this geographical distribution is shown in Fig. 1.
The second principal component is put together chiefly in information of humidity and temperature of warm season, and this geographical distribution is shown in Fig. 2.
The third principal component is put together chiefly in information of precipitation of warm season and annual temperature, and this geographical distribution is shown in Fig. 3.
Further, accumulated contributory rate of these three components is 71 percent.
Three-dimensional space, which is made from those components meeting at right angles, is divided in 14 groups (namely 14 climatic types), and mean scores of groups and distance of each group are shown in Table. 3. Roman numerals of group names are distinguished by score's sign of the first and second principal components. English characters are distinguished by score's sign of the third principal component, and subscript numbers are small classifications.
Those climatic types are plotted on the map of Tohoku district, and the map is divided into 21 small climatic areas. Also, 21 areas are united 9 zones (shown in Fig. 5).

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In the previous papers, one of the authors reported that the rate of photosythesis depends on the thickness of the boundary layer on leaf surface. In this connection, it is quite important to clarify whether the structure of air flow in the boundary layer is laminar or turbulent because the diffusive resistance for CO₂ toward leaf surface from atmosphere is greatly dominated by the structure.
Then, a wind-tunnel experiment was carried out and mean and fluctuating speeds of air flow in the boundary layer were measured by a hot-wire anemometer changing the free stream turbulence from 0.3% to 8% at Reynolds numbers (based on the distance from the leading edge of leaf) up to 10⁴.
(1) In the case of the free stream parallel to leaf, the boundary layer remains laminar irrespective to the values of free stream turbulence.
(2) In the case when the flow separates from the leaf at the leading edge, the boundary layer becomes turbulent downstream of the part of separation irrespective to the values of free stream turbulence.

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Light transmission in the greenhouse is an important factor influencing the design and layout of commercial greenhouse enterprises, since the quantity of solar light is quite often the limiting factor for plant growth in the greenhouse during winter months in Japan.
Recenty several workers have developed mathematical models which are capable of predicting the light transmission of greenhouses. While these models have been of great value, most of them have not considered the width and depth of the structural element, the shape of a frame, and the arrangement of structural elements. Several experiments, on the other hand, have shown that the structural frame can account for 60 to 70 percent of the total light losses in the greenhouse, and that a relationship exists between the arrangement of structural elements and materials of a greenhouse and the resulting distribution of transmitted solar light.
This paper presents an analytical approach to this problem. A frame with a glass sheet is considered as a fundamental element of greenhouse walls for analyzing transmission mechanisms of direct solar light into a greenhouse. The approach is based on a general model so that it can be adapted to any single greenhouse for which the light transmission characteristics and dimensions of each frame have been defined. But no provisions are made for internal reflection of light and for light diffusing covering materials in the present model. Models considering these effects have already been described in the other paper. Applications of the present model to complete greenhouses will be described in a later paper.
Transmissivities of solar light have been calculated of fundmental elements. The results obtained from this analysis show that the transmissivity for a fundamental element can vary widely with the dimensions of a frame and geometrical position of the sun (relative to the frame), and that the arrangement of structural elements has an important effect on the distribution of the daily integrated solar light in the greenhouse.
Some of the results for the paticular fundamental element whose dimensions are given in Figs. 3 and 5 are as follows:
1. The horizontal structural element running E-W direction constructing the south roof and wall causes an ununiform space distribution of the daily integrated light in the greenhouse.
2. The depth of a frame can account for 20 to 30 percent of total light losses in the greenhouse.
3. A higher transmissivity for a fundamental element is obtained in a greenhouse with square frames than with rectangular one.
4. The transmissivity of a vertical fundamental element whose azimuth is south is 82% in winter and 42% in summer.

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In the previous paper (HASEBA and TAKECHI, 1972) various patterns of the change in transpiration with wind speed were analytically explained from the solution of the energy-budget equation of a plant leaf.
In this paper, relations between the transpiration and the short-wave radiation are presented after the simulation of stomatal transpiration by taking into account the effect of insolation on stomatal aperture, and air temperature dependence of transpiration is also shown by reflecting over the joint effect of temperature on stomatal aperture. Further the obtained results are compared with some observations.
When the leaf-moisture available for transpiration is sufficient, an equation of the stationary heatbudget of a leaf with equivalent stomata on both surfaces is written as follows:
μR_s+β_L(R_l↓+R_l↑)-2β_Lσθ_L⁴=2h_BΔθ_L+2LD_TRΔC_L,
where R_s; short-wave radiation income, R_l↓ and R_l↑; long-wave radiation incomes from the upper atmosphere and the lower surroundings, respectively, and R_l↓=σ'Θ_A⁶ and R_l↑ is approximated as β_LσΘ_L⁴, Θ_L and Θ_A; temperatures of leaf and air(°K), respectively, Δθ_L; temperature difference between leaf and air(°C), ΔC_L=C_o+C(Δθ_L); water-vapor concentration difference of leaf interior from the surrounding air, C_o; saturation deficit of air in concentration, C(Δ_θL); correction term in vapor concentration difference due to temperature difference between leaf and air, μ and β_L; leaf absorptivities of solar and thermal rediations, respectively, σ; Stefan-Boltzmann's constant, σ'=1.27×10^-17ly/s°K⁶, L; latent heat of evaporation, h_B=h_n+h_f; heat transfer coefficient for leaf surface, D_TR=D_LDB/(D_L+D_B); transpiration-transfer-coefficient, D_L; internal transfer coefficient being a function of stomatal aperture, D_B=D_n+D_f; vapor transfer coefficient in boundary layer, h_n, D_n; effects of buoyancy on the boundary layer transfer, both are functions of temperature difference between leaf and air and vapor concentration difference, hf, Df; forced-convection transfer coefficients including the effects of leaf-temperature variation over the surface and turbulent air-flow within a plant canopy.
The heat-budget equation that contains unknown temperature difference between leaf and air in the terms of the outgoing long-wave radiation, free convection transfer and vapor-concentration difference was solved by using an analogue computer.
Transpiraiton rate (w) is obtained by the following formula: w=2D_TRΔC_L.
I. Relation between transpiration-rate and short-wave radiation.
When internal transfer coefficient was a function of insolation, transpiration was calculated in the range of short-wave radiation between 0 and 1.5ly/min, for various values of relative humidities ranging from 20 to 100% under fixed conditions of air temperature from 0 to 40°C and wind speeds of 0.2 and 1m/s.
Results obtained are as follows:
1) Increasing insolation which enlarges stomatal opening increases the transpiration. This change in transpiration is relatively strongly dependent upon the changes in stomatal aperture.
2) Except for the case of very low

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