To estimate the sunlit leaf area in the broad leaf plant community, solidgeometrical arrangement of each leaf was measured, and this shape was projected on the plane vertical to the direction of sunlight, and the sunlit or shaded area were calculated by Monte Carlo method using computer CDC 3600.
Tobacco plant in maturing stage was used as a material for this study.
1) Preliminary tests were carried out to determine the required time of random number for hitting each leaflet.
One square and a inscribed triangle were assumed (area ratio : 0, 5) and this figure was hit by 10, 100, 1, 000 and 10, 000 random numbers and examined the preciseness of estimation by triangle area.
The results indicated that hitting 1, 000 times for each leaflet may be enough for estimation (Table 1) .
2) For each calculation solar azimuth and solar altitude were predetermined, and normal incident solar radiation was assumed as I₀ =1 cal/cm²⋅ min.
3) Each leaf was divided into four to eight triangles, and each point of triangle was shown by χ, y, z orthogonal coordinate. The bottom of the plant was chosen as the origin, z as the vertical axis and y axis directed east.
4) χ, y, z coordinate axes were transformed to X, Y, Z coordinate, here Z axis directed to the sun from origin, Y axis was vertical to Z and on the χ, y plane. X axis was orthogonal to Y and Z.
5) Every triangle leaflet was projected on X, Y plane and if we select a specific triangle A_i (i=1, 2, ......), A_i may be shaded by other triangles B_j that have larger Z value. If we indicate nonshaded area of A_i as a_i, total sunlit area will be shown as nΣi=1a_i⋅ 1, 000 random numbers were produced to hit every triangle leaflet and a_i was estimated by the random number that reached A_i without disturbed by Bj. We could also judge the direction of the sunlight on the leaf surface or the lowersurface.
Monte Carlo method was adopted to estimate the sunlit leaf area of tobacco plants. The results indicate that this method will be promising to estimate the solar radiant accepted by many kinds of plant or plant community models.
Solidgeometrical arrangement of tobacco leaves and the model for this study were shown in Fig. 3. The leaf area of the model was about 77% of actual tobacco (Fig. 4) . Calculation was carried out in three cases, in which solar altitude was predeter-mined as 77°, 60°, and 30°.
Total solar radiant received by all leaflets was not so different in three cases and ranged 217-248 kcal/h, but according to the change of solar altitude, the distribution of sunlit area varied by leaves of different stalk position. The variation was largest in the altitude of 77° (Fig. 5 and 6) .
Calculation showed that in the case of solar altitude of 30°, the leaves that arranged parallel to the direction of sunlight, occasionaly received the light on lower surface.

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It is important for the studies on the relation of soil-water system to plants that soil water holding capacity is discussed on a view of pF curves.
Fresh soil particles change their nature of water holding capacity when they are dried to air-drying state (≅pF 6) . On the contrary, before air-drying the change of soil water holding is based not one the changes of the water holding capacity but on the structural changes of soil particles. Namely, when not dried so intensely as air-drying, soil. particles do not change their nature of water holding capacity, but they gather themselves to make massive particles. As massive particles have less specific areas which hold water than individual particles, soil water holding capacity decreases on increasing a proportion of massive particles in soil.
Massive particles once gathered are not dividedd to individual ones adding water again, then soil, as. a whole, seems to decrease as much water content as specific areas decreased. But, when massive particles are dispersed by supersonic wave, they become individual ones and have same water holding capacity as fresh soil particles. Once air dried, soil particles have different nature of water holding capacity from one of particles of same fresh soil.

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1) Two experimental populations were made each with about 1, 000 F₂ flies of 192 female flies collected from natural populations of Drosophila melanogaster at Kofu and Katsunuma in Yamanashi Prefecture.
One population (F population) has been maintained in a population cage in the incubator “KOITOTRON”, in which the temperature was regulated by a program controller so that it fluctuated two times a day between 20 and 30°C (f environment) . The other population (C population) has been maintained in a population cage in the culture room, in which the temperature was kept constant at 25°C (c environment) . These two populations have been maintained for about two years and flies used in the experiment were sampled from them randomly.
2) Flies sampled from C population were exposed toc environment (C-c group) and to f environment (C-f group), and flies sampled from F population were exposed to f environment (F-f group) and to c environment (F-c group) . Longevity of female flies (Exp. I), fecundity (Exp. II, III) and egg to adult hatchability (Exp. IV, V, VI) were estimated under constant and fluctuating temperatures and the results for the four groups were compared.
3) The mean longevity of female flies in F-f group was 31.3 days and that in C-c group was 29.0 days. The longevity in constant environment was generally shorter than in fluctuating environment, but the mean longevity of female flies in F-c group was remarkably short being 25.7 days.
4) Fecundity and longevity are closely related quantitative characters. Mean longevity of female flies in constant environment was shorter, but their mean fecundity was superior to that of female flies in fluctuating environment. Especially, young female flies (until 10 days after emergence) in C-c group laid significantly more eggs than in C-f group. However, the total number of eggs laid by female flies during 40 days in F-c group which showed the shortest mean longevity, was smaller than in other groups.
5) Egg to adult hatchabilities of young 1-10 days old female flies of the four groups were higher than 90 per cent and no difference was found between them. However, the hatchability of C-c group decreased faster than in other groups with the age of female flies advancing to 15 and 20 days, and that of 20 days old female flies was 61-67 per cent. On the other hand, the hatchability of 20 days old female flies of F-f group was kept at 71-81 percent and those of the other two C-f, F-c groups were almost intermediate.
6) Longevity, fecundity and hatchability are thought to be important components of fitness in Drosophila. These quantitative characters are controlled by polygenes. When the variances in these characters of the four groups were calculated and compared with each other, homeostatic gene systems of flies in F and C populations cultured under fluctuating and constant temperatures were revealed and the grade of homeostasis of the former was. considerably higher than the latter. Especially, the manifestations of these characters in F population were very unstable and widely fluctuating under constant temperature and the cause of the result was discussed.

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