PLANTS OF NORTHERN GUJARAT. 
215 
During April and May westerly or south-westerly winds prevail 
through the local indraught from the shores of the Arabian Sea, and 
humidity rises a little. In June the wind is changeable owing to the 
general disturbance of the climate which precedes the setting in of the 
monsoon. From July to September the climate is under the influence 
of the south-west monsoon drift, varied by the passage westward of 
occasional cyclonic storms from the Bay of Bengal. The drift is, how- 
ever, much less vigorous and the temperature consequently much higher 
than in the Konkan or Deccan. In October and early November the 
wind is again changeable. From late November to January northerly 
winds blow down from the Himalayas, but these as they have ;,o pass 
over a wide land area before they reach us are far less cold than in the 
Punjab or Sind. Indeed there are few days in the winter when the 
cold is at all noticeable. In February and March dry and changeable 
winds prevail. 
Temperature has been partly indicated above. The actual maximum 
ever recorded at Ahmedabad is 120° (in May 1912), and the ordinary 
annual absolute maximum is from llb° to 117°. These are, of course, 
readings far lower than those of the Punjab or even the United Provinces. 
But on the other hand, our winter temperatures both by day and 
by night are far higher. Frost occurs at ground level very rarely 
indeed, say on one night in ten years. Consequently, the mean annual 
temperature of the country from Ahmedabad to Deesa (the latter station 
being slightly warmer) is one of the highest in India. We have not 
taken any readings of the temperature of the soil, but there is no doubt 
that in the hot weather it is very high, and having regard to the light 
sandy nature of the surface soil and its great depth there is every reason 
to believe that if a series of readings could be taken of the temperature 
at depths from one to three feet or more it would be found that in no 
part of India is the permanent mean temperature of the soil higher than 
in the sand tract of North Gujarat. 
It will be necessary to refer to the climate again in the next 
paragraph, . 
5. Vegetation. 
Perhaps the most interesting feature of the vegetation is that it 
marks the dividing line between the Perso-Arabian flora (to which the 
flora o'* Sind belongs) and the Indo- Malayan flora proper. Drijdb, in the 
map in his Handbuch ber Pflanzengeographie, 1890, makes the line 
of demarcation pass up through the gulf of Cambay northward along the 
Aravali Hills, thus exactly traversing our area* Our own list is in close 
