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THE JOURNAL OF INDIAN BOTANY. vegetational seasons. From the point of view of the vegetation it is convenient to begin the year with the rainy season (Fig. 7). This season may be taken to begin about the 15th to the 20th of June, when the first scattering rains fall, and lasts to the end of Septem- ber. It is characterized by high rainfall, low insolation, high tem- perature, and high humidity (Table V, and Figs. 4 and 7). July may be taken as typical of this season, when the mean temperature range is from 80.6° to 89.2°F., while the relative humidity ranges from 89.3 to 71. 7 per cent. Such conditions are optimum for plant growth, and a luxurient herbaceous vegetation springs up.

The rainy season merges gradually into the cold season, which may be taken to extend from the first of October to the end of February. It is characterized by low rainfall, high insolation, low temperature, and relatively high humidity. December may be chosen as a typical month ; the mean temperature range is from 48.6 to 74.2°F., and the relative humidity runs from 88.4 to 40.5 per cent. (Table V, and Figs. 5 and 7). The lower temperature and the low

Fig. 5. Mean hourly temperature in degrees Fahrenheit and mean relative

humidity in per cent, for the month of December at Allahabad. Fig. 6. The same for the month of April.

humidity of midday result in a vegetation that is mesophytic, and which contains a larger proportion of temperate region plants.