132 



The Plant World. 



much higher than in continental desrts, but it makes it rela- 

 tively constant throughout the day and throughout the year. 

 Half the annual average rainfall comies in two seasons, in May 

 and June, and in October, the mid-winter and mid-summer 

 being very dry. In spite of this unequal annual distribution 

 of the rainfall the average monthly humadity of Kingston reach- 

 es no lower a irinimum than 75 per cent, in April, and the an- 

 nual average is 78 per cent. The writer has taken a number of 

 humicit}' readings with a sling psychrometer in the deserts near 

 the shore and at som.e distance back from it. These ranged from 



Fig. 2. 



A pure stand of mesquite, or cashew (Prosopis juliflora), in the savannas near 



Kingston Harbor. 



74 to 77 per cent, in other words they were not far from the 

 m.onthly averages for the weather station in Kingston. It was not 

 practicable to obtain humidity readings at night, but it is prob- 

 able that the falling of the sea breeze is counterbalanced in its 

 effect on the humidity by the cool land breeze from the moun- 

 tainous interior (locally known as the "doctor"), and by the 

 fall in temperature during the latter hours of the night, re- 

 sulting in a relatively level daily humidity curve. 



