90 PLANT HABITS AND HABITATS IN THE 



cropping ' rocks at Wynbring, west of Tarcoola, and to the ancient 

 rocks to the west of Nullarbor Plain in Western Australia. 



The soil in the immediate neighborhood of Tarcoola is various. 

 On the hills it appears to be very coarse and on the adjacent plains 

 there is a large admixture of sand brought from the higher ground. 

 In places there is to be found clay, or at least soil of a very fine char- 

 acter resembling clay, and also a white subsoil, apparently travertine 

 or desert limestone. Some sandy stretches to the north of the Adllage 

 are of very considerable extent; and, finally, there are depressed 

 areas, of various sorts, in which the soil carries a large amount of salts. 



With the differences in soil and in topography are associated differ- 

 ences in the water relations as well, and without doubt a close study 

 of the vegetation of the region would reveal a variation in. its flora 

 intimately connected with such differences in the subterranean en- 

 vironment. 



Rainfall and Tempebatubb. 



The rainfall at Tarcoola averages 7.71 inches over a period covering 

 9 years, but the variation from year to year is considerable. Thus 

 the highest recorded (1910) was 12.35 and the lowest (1905) was 2.82 

 inches. The record for Tarcoola in 1912 was 6.43 inches. There 

 were 33 wet days during the year. The wettest month was July, 

 during which 1.8 inches of rain fell. On March 9 of the same year 1.12 

 inches of rain occurred. The type of raiafall, therefore, conforms to 

 that of the other arid stations visited. In 1912 at Port Augusta 

 10.92 inches of rain fell during 66 days. It will be seen, therefore, 

 that an average of 0.19 inch occurred each rainy day at Tarcoola and 

 only 0.16 inch at Port Augusta. It is of interest to note that at Oodna- 

 datta the average daily, amount during rainy days was 0.15 inch and 

 at Copley (Farina) 0.24 inch. Inasmuch as the penetration of the 

 rains is, other conditions being equal, directly connected with the 

 amount of the rain, it would appear, so far as the year 1912 is con- 

 cerned, that the rain penetration at Tarcoola was probably fairly, 

 at least relatively, good. About 65 per cent of the rainfall at Tarcoola 

 occurs during the cool season, April to October, while the percentage 

 at Port Augusta is for this season somewhat greater, being approxi- 

 mately 75 per cent. 



The summers at Tarcoola are hot and the winters cool, as would be 

 expected from the situation of the place. Mr. Harry Deadman, of 

 Tarcoola, who is well acquainted with its climate, informs me that the 

 summer maximum shade temperature is about 118° F. The tempera- 

 ture is greatly influenced by the desert-arid region to the north and 

 by the Bight to the south, though the latter is about 100 miles distant. 

 Summer winds from the north are extremely hot as well as dry, while 

 those from the south, in summer, quickly cause a lowering of the tem- 

 perature. 



