395 



during the preceding seasons, and the heaviness of the stocking. Naturally, 

 land that has been "spelled" for a season or two with no sheep upon it, and 

 only browsed upon by occasional kangaroos, shows much denser growth of 

 bushes than an area carrying sheep. 



The individual bushes grow erect and branch freely, the leaves are 2-5 cms. 

 long and about 1 cm. broad, somewhat succulent, with a scurfy covering of 

 fleshy hairs. Associated with A. vesicarium may occur other half -shrubby 

 species such as A. stipitatitm and A. palndosiim. Annuals are many, but their 

 abundance and type depend upon the season at which a heavy rain has occurred. 

 Following summer rains grasses, especially Stipa spp., are most abundant. The 

 plants most prominent in Spring are chiefly Compositae, e.g., Helichrysum 

 polygalifolium, H. hyalospermum, etc., and Cruciferae, e.g., Erysimum lasio- 

 carpum. PL xxxv., fig. 1, shows a view of a typical Atriplex vesicarium com- 

 munity. It will be seen that the plant covering is remarkably uniform, even to 

 the horizon about two miles away. The soil of this area on Koonamore Station 

 is analysed as sample 1. It will be seen from the table that the soil when 

 collected was dry, but that the moisture at saturation (38'5 per cent.) indicates 

 a fair water-retaining capacity. The total salts were only 1 per cent, of the dry 

 weight, of which only 05 per cent, was chlorides. Soil sample 2 is from a 

 similar community, but collected four months previously at Dilkera, approxi- 

 mately 120 miles to the south. The essential similarity between the two soils is 

 apparent. 



Mallee (Eucalyptus oleosa) with saltbush. 



This community consists of a mallee scrub with an undergrowth composed 

 largely of saltbushes. Various eucalypts are involved, but E. oleosa is most 

 abundant. The plant is a typical mallee, growing from a large subterranean root- 

 stock, with several equal trunks, especially in the young stages. Older plants 

 are more tree-like with perhaps but a single trunk arising from an enlarged 

 subterranean base. The height varies from 15-30 feet or more. The leaves 

 have the usual pendant habit of eucalypts and are clustered at the end of the 

 branches, so that the characteristic canopy top is produced (pi. xxxv., fig. 2). 



Other trees or tall shrubs associated with the mallees are: — 



Exocarpus aphylla Heterodendron oleaefoUum 



Fusanus acuminatus Lycium australe 



Acacia Oswaldii Myoporum platycarpimi 



Templetonia egena Pholidia scoparia 



These 2.re all subordinate to the mallee in this community, though locally 

 some of them, e.g., Templetonia or Pholidia, may become so abundant as to give 

 a distinct facies to the area. The undergrowth is of Atriplex vesicarium, with 

 A. paludosum or A. stipitatum or locally Kochia sedifolia. The bushes are 

 generally smaller and more scattered than in the community previously described. 

 They are, however, sufficiently numerous to give a definite character to the 

 vegetation, which thus differs from mallee communities, such as are developed 

 further south and outside the area under investigation, by the presence of salt- 

 bush and the more open growth of the mallee. 



Soils from this community are Nos. 3 and 4. Comparing No. 3 with No. 1 

 (pure Atriplex), collected on successive days about 50 miles apart, it will be seen 

 that they are very similar, except that the mallee saltbush soil was drier, has a 

 slightly lower percentage of water at saturation, and possesses nearly twice the 

 amount of soluble salts (18 per cent.). The percentage of chlorides in the two 

 soils is identical. Indeed, samples 1-4, although taken at different times and 

 over a wide range of country, agree remarkably. 



