304 



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 



2 A 6 3 IO 12. 14 lb I a 2o XZ ZA 2 A 6 8 10 iZ 14 16 16 Zo 22Z4 



Hour 3 of tJje day Hours of t>>» day 



Fig. 5 Fig. 6 



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. 



