ARID PORTIONS OF SOUTH AUSTRALIA. 



17 



70% 



^ 



FIG. 76. Mean humidity of Australia for July, after Taylor, 1918. 



absence of data dealing directly with the subject we may get some idea 

 of the amount of light as well as of its variation in amount over the 

 continent by comparing the number of hours of sunshine at several 

 representative stations (table 5). 



TABLE 5. Hours of sunshine for representative stations in Australia. (Hunt, 1912 : 625.) 



There is an interesting relation between the light and the reaction of 

 the plant to other environmental factors. In regions having little 

 rainfall especially, the exposed surface of plants is reduced in extent so 

 that the amount of water lost is thereby also reduced. This is carried 



