238 THE JOURNAL OF INDIAN BOTANY. 



The average rainfall in the Sat Tal valley as recorded by Mr. 

 A. 0. Evans, proprietor of the estate, for the eight years from June, 

 1913 to May, 1921 was 85.02 inches. This corresponds pretty 

 closely with the figures in the Naini Tal Gazeteer for the rainfall at 

 Kathgodam at the foot of the outer range, 91.27 inches, and at Naini 

 Tal about five miles from Sat Tal to the north-west and at an altitude 

 of about 7000 feet, 97.49 inches (8). These places all lie in a general 

 way on the outer slope of the outer range, for the highest peak of 

 Sat Tal is at the north of the valley. The inner valleys of the 

 Himalayas have considerably less precipitation. 



The altitude above which frost is severe enough to affect vegeta- 

 tion is approximately 4000 feet. Sat Tal has an occasional hoarfrost, 

 but the temperature rarely gets down to the freezing point. 



Seasonal Periodicity of Vegetation. 



The distribution of the rainfall by months is shown in Fig. II, 

 84 per cent, of the rain falls in four months — June, July, August and 

 September. Hence there is in all the formations a striking seasonal 

 periodicity based on the water supply. This is most marked in the 

 lower or monsoon forest formation where the effect of the dry period 

 is most intense. At the beginning of June, vegetation is at a compa- 

 ratively low ebb, the monsoon forest trees being leafless and herbs 

 being not much in evidence. With the first rains there is a marked 

 revival of activity. The trees which have to this time remained 

 leafless burst into leaf, a wealth of annual and fleshy rooted perennial 

 herbs spring up, and there is germination of many tree seeds upon 

 the forest floor, e.g., those of the Bauhinias. 



With the close of the rainy season much of the herbaceous 

 vegetation ripens its seeds and dies to the ground. October brings 

 a wealth of composite and labiate herbs, including goldenrods, asters 

 and groundsels, which remind one of the forest floor of a climax oak 

 forest in Europe or America. Already some of the monsoon forest 

 trees such as Bombax malabaricicm, Qaruga pinnata, and Erythrina 

 suberosa are losing their leaves. Winter deciduous trees of the oak 

 forest, such as Primus pucldum and Pyrus pashia, become leafless 

 about the same time. No part of the winter is too cold for the vege- 

 tative activities and even for the flowering and fruiting of much of 

 the vegetation. Prinsepia utilis, a widespread pioneer rosaceous shrub 

 of the oak forest, has festoons of blossoms in midwinter. About Feb- 

 ruary the candle-like spikes of Sapium insigne appear. 



From March to May is the hot season. Trees blossom profusely 

 during the early part of this season, conspicuous among them being 

 the legumes of the upper monsoon forest. Bauhinia variegata puts 



