The mathematical treatment of the temperature regime of the soil profile may be said to be founded upon a assumption of a homogeneous soil bounded with simple conditions, for instance, the soil surface temperature fluctuated sinusoidally and the average soil temperature over the whole layer was the same, having no relation to the depth. However, in the greenhouse field, we observed that the soil compositions were different among the layers, that is, the soil was formed from the various layers, so that the average of the soil temperature given diurnal variation showed different value in every depth. We always obtained the above facts.
The complicated changes of the diurnal soil temperature did not agree with the results from the mathematical treatment. This disagreement required to make the measurement at the field high sensitive. However, the reason of the disagreement was clarified to be the traditional mathematical treatment based upon the simple assumption.
In this paper, the theory was investigated in detail to determine the thermal diffusitivities in various layers of a soil from the values of diurnal change of the soil temperature. The theoretical equation was derived to express the equation (29) . Using this equation, the procedure to gain the thermal diffusivity was explained in the Table.

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Maskmelons cultivated in four types of root medium which are NFT, water culture with gravel, kuntan composed with carbonized chaff and soil, are examined from seedling to harvesting stage. The research is done in a greenhouse where environmental condition of roots and shoots are controlled by a microcomputer system.
In planting stage, it takes different days for taking root among them. Especially, growth of root systems in mass medium such as soil and kuntan is better than that in water culture or NFT, because the balance between water retentivity and air permeability in these mass mediums is kept effectively and roots in them are protected from the surrounding disturbance. On the other hand, these in water culture or NFT are a little bit worse. After all, that in NFT is worst. These may be caused by what the roots are exposed to surrounding atmosphere without any supporting body.
In vegetative stage, growth in mass medium shows the same favorable progress as in the previous stage. Furthermore it should be kept in mind that roots and shoots in NFT begins to grow quickly in this stage. It may be caused by the best air permeability among these four types of root medium.
In reproductive stage, NFT produces most favorable quality of fruit because the air permeability in it is best among them. Maskmelons in kuntan or water culture, however, show remarkable root-rot based on the worse condition caused by reduced air permeability in this stage, accompanied by the much improved phe-nomena of aging in roots and much more poor yields.
It may be evident that maskmelons have best yield in NFT. NFT seems to be reasonable from the point of view of control engineering, because the manipulation of both water supply and drainage in NFT system is most easily controlled.

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The effective characteristics of spectral reflectivity for evaluating chlorophyll content on a leaf areal basis were investigated in eight species of dicotyledonous trees and in sweet potato. Using regression equation between chlorophyll content and reflectivity ratio of rNI'/rG', where rNI' and rG' are the spectral reflectivity at 800 nm and 550 nm, respectively, the chlorophyll content of the leaf was estimated in May to December. The obtained value showed the standard error of about 5μg⋅cm^-2, which is about 10% of the mean chlorophyll content of all leaves examined (sample size: 147), irrespective of species and seasons. The correlation equation for the estimation was different from that for monocotyledonous plants reported previously.

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The seeds of Shorea robusta Gaertn. f. are economically important to the forestry as well as the food oil in India. The freshly harvested seeds of Shorea robusta lost their germinabilities (germination ability) 10 days after harvest at room temperature (25°-30°C) . However, the seeds could be kept in viable condition for two months after harvest at cool temperature (10°-12°C) . Under this chilling condition, the seeds were entered in dormant state (secondary dormancy) which maintains the seed longevity for a longer period. The water uptake and the germination of the seeds, which are classified into categories 1, 2, 3, and 4 from morphological characters, show that cool temperature is one of the criteria to induce the secondary dormancy due to altering the seed membrane from permeable to impermeable. Based on the results of this study, it is possible to preserve the seed viability for a longer period of time which will help the plantation of this economically important plant.

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The spectral reflectivities above a forage canopy of plant populations were measured at seven wavelength bands between 417-800 nm under artificial light for determining the most effective spectral reflection characteristics applicable to the remote sensing of total chlorophyll content in a unit land area and leaf area index of a plant community. Model canopies for nine species (specific names were written in the legend of Fig. 2) were made in a laboratory with stems or branches. Fifty six kinds of indicies, which are seven spectral reflectivities, the reciprocals of them, and the ratios between any two spectral reflectivities, were chosen as spectral reflection characteristics. The regression analyses between these spectral reflection characteristics and total chlorophyll content in a unit land area and leaf area index of the model canopies were carried out. The obtained results showed that the effective spectral reflection characteristics was rNI/rR, where rNI and rR are spectral reflectivity at 800 nm and 660 nm, respectively.

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