8 



PLANT HABITS AND HABITATS IN THE 



FEATURES OF THE CLIMATE OF AUSTRALIA. 



RAINFALL. 



There are four major rainfall regions in Australia, according to Taylor 

 (1918 2 : 10), namely, the summer-rain region of the north, the winter- 

 rain region of the south, a region of uniform rains in the east, and a 

 region of little rain in the center and middle west. The seasonal 

 shifting of the climatic complex north-south, following the declination 

 of the sun, operates to bring about the seasonal rains. Tropical storms, 

 cyclones, reach inland in summer and cover the entire northern portion 

 of the continent. They extend south barely as far as Oodnadatta. 

 The winter storms, on the other hand, affect the southern portion and 

 extend north only about as far as Farina, South Australia (Taylor, 

 191 8 2 : 10) . These accompany the northern extension of the prevailing 

 westerlies which in summer are far to the south of Australia. There is, 

 therefore, a belt of territory running roughly east and west which is 

 beyond the usual reach either of the winter or of the summer rains. 

 This dry central region comprises, according to Taylor, 37 per cent of 

 the area of the continent. 



TABLE 1. Rainfall at the capitals. 



The leading characteristics of the rainfall in the humid regions can be 

 illustrated by that at the capitals of the different states. These are 

 summarized in table 1. At Adelaide and at Perth rain occurs mostly in 

 the winter season; at Brisbane it is mostly in summer; at Sydney it is 

 mostly in late summer, autumn, and early winter, while at Melbourne 

 and at Hobart it is fairly evenly distributed throughout the year. 



So far as the well-being of the vegetation as a whole is concerned the 

 reliability of the rains (or the want of this) is of capital importance. 

 And in a general way the reliability of the rains decreases with the 

 decrease in the amount of the rainfall, which it will be seen only serves 

 to intensify the effects of progressive aridity. Thus we find that in the 

 dry interior of the continent there is a mean variation equal to 40 to 50 

 per cent from the normal (Taylor, 1918 1 , fig. 4.) In some years very 

 little rain falls at any season, while in others almost the entire yearly 

 rain may fall within a few hours. While the rainfall throughout the 

 interior is as a rule very unreliable, the portion of the dry mid-region 



