The term of “neyuki” (continuous snow cover) had been used rather vaguely, before a definition was put on the term by the Japan Meteorological Agency in 1959. Accordingly, it is difficult to obtain the correct information on the inter annual variation of the last date of “neyuki” for the periods from beginning of observation to the present time.
This study was made to obtain an empirical formula for estimating the last date of “neyuki”.
In the analysis, the author observed that the use of daily maximum air temperature gave smaller errors of estimate of snow melt than daily mean air temperature, when the daily mean air temperature was lower than about 0°C.
The simple formula for the last date of “neyuki” y was obtained as the function of mean daily maximum temperature in March θ and maximum snow depth in March x. The inter annual variation of the last date of “neyuki” in each place of Hokkaido, which was calculated using the formula, is shown in Fig. 4 with that obtained through the climatic data. As can be seen in Fig. 4, there was large difference between two curves in Abashiri, Asahikawa and Sapporo before 1920, and in Obihiro before 1940. This result shows that the use of values of the last date of “neyuki” recorded in climatic data in those days may lead to noticeable errors.
Judging from the estimate in Fig. 4, the last date of “neyuki” seems to have been early in the 1900's, 1930's and 1960's, and to have become later since the later 1960's.

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Direct and diffuse components of solar radiation were measured inside and outside a single cylindrical vaulted greenhouse. The greenhouse oriented quasi-north-south, had been constructed with thin steel pipes (1.9cm dia.). The inner surface of the polyvinyl chloride film (0.1mm thick) which is the covering material of the greenhouse had been wet with dew, under the same conditions as normal cultivation greenhouses.
The direct solar radiation transmitting the cylindrical vaulted greenhouse was calculated theoretically, and it was compared with actual measurements.
The differences in inside direct radiation between the greenhouse with the new film and that with the used film, were investigated.
1. Results of observation.
The components of direct and diffuse radiation inside and outside the greenhouse were expressed as follows:
τ(Q+q)=(τ_Q+τ′_Q)Q+τ_qq=τ_QQ+τ′_QQ+τ_qq
where, Q+q: outside total radiation (direct solar radiation plus diffuse sky radiation), τ(Q+q): inside total radiation, τ: inside/outside ratio of total radiation, τ_QQ: inside direct radiation, τ_Q: inside/outside ratio of direct radiation, τ′_QQ+τ_qq: inside diffuse radiation (effective scattered component of direct solar radiation plus transmitted diffuse sky radiation), τ_q: inside/outside ratio of diffuse sky radiation, τ_Q: effective scattering coefficient of direct solar radiation. The numerical values in the formula were obtained on a clear day. Assuming that the inside/outside ratio of diffuse sky radiation is equal to the inside/outside ratio of total radiation on an overcast day, we have τ_q=75% as an average (Fig. 1). Inside direct radiation is lower than outside (τ_QQ<Q), conversely, inside diffuse radiation is higher than outside (τ_Q′Q+τ_qq>q). The intensity of τ_Q′Q is equally matched for τ_qq, and it cannot be disregarded even in the transparent plastic greenhouse. The value of τ increased from 56.0% in January to 60.2% in February. The increase of τ depends on the increase of τ_Q from 30.8% to 37.9%, despite a little decrease of τ′_Q from 20.3% to 18.6% (Fig. 2). It appears that the seasonal variation of inside/outside ratio of total radiation is mostly affected by inside/outside ratio of direct radiation.
Generally, the transmissivities of direct solar radiation in the polyvinyl chloride films have a tendency to decrease with increasing angle of incidence (Fig. 4). The tendency of dirty film, contaminated by dust in the city, is steeper than that of new one. Moreover, this tendency is the most remarkable of dewy film now in use.
2. Consideration of inside/outside ratio of direct radiation.
An equation was deduced for calculating the solar incident angle on a curved surface of cylindrical vaulted greenhouse. The angle of incidence I is written as follows:
I=cos^-1|sin h⋅cosecω⋅sinρ|
ρ=tan^-1{√sec²ω-k²/k}
ω=tan^-1(cosecθ⋅tan h)
excepting that the angle I=90°-h for θ=0, and ρ=90° for k=0. Where, h: solar altitude, θ=α-α′: angle between solar azimth α and greenhouse orientation α′, k=l/r: ratio of ground level above the center of cylinder l to radius of greenhouse section r (Appendix Fig. 1).
Diurnal variations of direct radiation inside the greenhouse under observation were calculated by using I in the above equation with the values of k=0.4 and α′=

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Seedlings of 57 species (35 species for C₃-plants, 22 species for C₄-plants) were used for the measurement of increment of plant height during 25 days under submerged and upland conditions, and those of 24 species (15 species for C₃-plants, 9 species for C₄-plants) for the relationships between temperature (12-48 C) and photosynthetic rate under submerged and upland conditions.
The results are as follows:
1) All C₃-winter plants were died except Welsh Onion under submerged condition and most of C₄-plants had greater growth increment under submerged condition than that under upland condition. C₃-summer plants had the character intermediate between C₃-winter plants and C₄-plants. That is, only few C₃-summer plants were died under submerged condition. Most of C₃-summer plants were not died, and had less growth increment under submerged condition than that under upland one.
2) When the plants grew under submerged condition, the photosynthetic rate of all C₃-winter plants was decreased. But the rate of most of C₄-plants decreased a little or increased. C₃-summer plants had the character intermediate between C₃-winter and C₄-plants.
3) As for the photosynthetic rate, C₄-plants had a strong heat tolerance and a comparatively strong wet endurance. While C₃-plants had a comparatively strong cold resistance and a wide range of wet endurance. Based on the above results, we discussed the origin of rice (Oryza sativa L.).

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Changes in transpiration rate, leaf water potential (ψ) and leaf diffusion resistance (R_L) were studied in potted satsuma mandarin (Citrus unshiu MARC.) trees subjected to a drought-rewatering cycle. Results follow:
1. ψ(ψ_max) measured before sunrise at which a decline in relative transpiration rate (drought tree/well-watered control tree) occurred was dependent on Δe (difference in vapor pressure between ambient air and saturated atmosphere at leaf temperature). Namely, under high Δe, the reduction in relative transpiration rate took place at a higher ψ_max (about -4 bars). When Δe was low, relative transpiration rate did not decline appreciable until ψ_max fell to a lower value (-7 to -10 bars).
2. Transpiration rate had high positive correlation with 7.15×10^-7Δe/R_L (r=0.984) and VPD/R_L (r=0.920). The ratio, VPD/R_L may be used as an estimation of transpiration rate in citrus orchards, because VPD (vapor pressure deficit) and R_L can be easily measured in the field.
3. ψ_min measured in the daytime recovered rapidly after rewatering in time of desiccation to -24.5 bars of ψ_max and exceeded more about 2 bars than that of the well-watered control tree for several hours, because recovery in R_L of the drought tree was incomplete. Both R_L and ψ_min returned completely to the control level at the same time.

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