ARID PORTIONS OF SOUTH AUSTRALIA. 109 



Physical and Climatic Features. 



The region west of Blanchtown, which Hes on the western bank of 

 the Murray River, is nearly level. However, it has the appearance, 

 although whether this is true in fact was not learned, of rising as one 

 approaches the river. 



In this characterization of the region Howchin (1909:95) says: 



" The greatest development of the coastal plains in South Australia is in 

 the southeast, between the central highlands and the Victorian border. It is 

 often spoken of in three sections : The Murray Flats, between the ranges and 

 the River Murray; the Ninety-Mile Desert, between the river and the 

 Victorian border, by the old stock routes; and the South-East or most south- 

 erly section. The physical features throughout are very uniform. Gently 

 undulating ground, with a few more prominent ridges ; light, sandy soil which 

 frequently changes to a travertine-limestone crust." 



The Murray Fkts, which were visited, forms a part of the great 

 Murray-Darling Basin, which is the most extensive river basin on the 

 continent. This basin probably should be considered as constituting 

 an important highway for the migration of plants. Stretching over 

 about 12° latitude, and thus including within its extent a great variety 

 of climate, it nevertheless is fairly consistent in having relatively 

 good water relations throughout. 



Rainfall and Temperature. 



Blanchtown is in the belt of winter storms. The average annual 

 precipitation is 10.77 inches. But at Blanchtown, as at other semi- 

 arid stations, there is not a little variation from one year to another 

 in the amount of the rainfall. The least recorded up to 1912 was 

 5.84 inches and the greatest was 19.71 inches. Thus, although at 

 times the rainfall may be considerable, it is nevertheless always 

 periodic, so that there is a marked season with no rains of moment, 

 or none at all, during which the perennial plants may be subject to 

 conditions of extreme drought. 



There are apparently no temperature records available for Blanch- 

 town. The nearest meteorological station is Kapunda, about 32 

 miles west. The altitude of the latter is 803 feet, and hence the tem- 

 perature conditions can not be taken as being parallel to those at 

 Blanchtown, although they are probably similar. However this may 

 be, the temperature for Kapunda may serve to illustrate certain fea- 

 tures of the climate of the mallee country to the west of the Murray, 

 and for this reason they are summarized in table 15, supplied by the 

 Commonwealth Bureau of Meteorology. It will be seen that the mean 

 maximum temperature at Kapunda is 71.1° and that the mean mini- 

 mum is 50° F. The highest temperature at the station recorded up 

 to 1912 was 113° and the lowest was 27° F. 



