340 H. I. JENSEN. 



glauca?) and two phylloclade bushes (Leptomeria aphylla 

 and Apophyllum anomalum) occur together with belar r 

 wilga and brigalow. 



The only herbs which seem to grow on typical gilgai 

 country in the natural state are members of the saltbush 

 tribe (Rhagodia species, R linifolia and others). 



The vegetation grows mainly on the hummocks sending 

 long surface roots into the depressions. The gilgai vegeta- 

 tion is characterised by abundant surface roots and an 

 absence of tap root. 



IV. The Soils of the Gilgai Areas. 



The soils of the gilgai country are mostly dark grey or 

 almost black clays which in appearance suggest a consider- 

 able degree of salinity. They resemble soils which have 

 been irrigated with saline artesian water for a period of 

 years. A small gilgai belt lying 10-12 miles south of 

 Cuttabri, on the track to Cubbo, has red clay soil, and 

 small patches of crabholey country also occur in the red 

 soil belt along Baradine and Dubbo Creeks. 



In mechanical composition (See Table A) the gilgai soils 

 are chiefly heavy stiff clays with a small percentage of 

 rather coarse sand. In dry weather they crack with the 

 formation of deep fissures just like the most heavy clay 

 soils of the Namoi Black Soil Plain. In wet weather they 

 are very boggy, and on drying they become as hard as 

 cement. A crowbar or pick has to be used to get a soil 

 sample. 



In the hummocks we find a layer of soil from six inches 

 to two feet from the surface in which white specks and 

 nodules, ranging up to the size of a pea, occur. These 

 white lumps consist of carbonate of lime, chemically pre- 

 cipitated. This precipitation of carbonate of lime in the 

 subsoil of the hummocks indicates a rise of salts by capil- 



