482 PROCEEDINGS OF SECTION D. 



areas, generally occupying the ridges, and never descending so far as 

 the alluvial flats. It shows a marked aversion for the soil upon which 

 E. albens grows, and the latter exhibits equal disdain for the company 

 of the stringybark. 



Another tree w^hich prefers a sedimentary formation is E. sider- 

 oxylon, A. Cunn., the mugga or ironbark of the western slopes and in- 

 terior, though it may sometimes be seen growing on decomposed granite 

 formation. 



THE INTERIOR. 



This division embraces all the western part of the State beyond 

 the western slopes, and similar country extends into South Australia, 

 Queensland, and the north-west corner of Victoria. The flora of this 

 area is decided chiefly by climate and rainfall, with important internal 

 divisions according to changes of soil. Owing to the low rainfall and 

 high temperature the conditions are dry and hot, and, in contrasting 

 the flora of this division with that of cool Tasmania, it may be mentioned 

 that not a single species of eucalyptus found in the interior is recorded 

 for Tasmania, where neither a true ironbark nor a box tree is found. 



The vegetation of the interior is more stunted than in other parts 

 of the State. A eucalypt 100ft. high is here regarded as a very tall 

 tree, the average not exceeding 50ft. or 60ft., with a gradual diminu- 

 tion in height as the far west is approached. Oyer much of the central 

 part, say around Bourke and Cobar, the forests do not average more 

 than 50ft. high. 



As climatic conditions, rainfall, and aspect are similar over a great 

 part of this division, the various changes in the flora may be regarded 

 as due to variations in the geological formation, or to the difference 

 between rocky and alluvial situations ; and some of these changes are 

 very marked. The hills are generally only a few hundred feet high, some 

 of them being composed of porphyry or granite, Avhile the sedimentary 

 ridges are either of sandstone or Silurian slate. Stretching for many 

 miles from the foot of these hills are almost level tracts of deep friable 

 soil, fine in texture, often reddish in color, and made up for the most 

 part from the weathering of the surrounding elevations. This class of 

 soil extends until it meets the river country, or what is generally known 

 as the black soil plains. The black soil is of a close, sticky nature, and 

 has apparently been spread over a vast area of the western country 

 in geologically recent time. Some of its properties are similar to 

 those of soils in mountain valleys which have been filled from the 

 weathering of basaltic hills, and it seems probable that the black soil 

 plains represent areas over which material from basaltic country has 

 laeen deposited. Rivers which drain granite or sandstone hills produce 

 alluvial flats with a loose soil, altogether different from that derived 

 from basalt, and having a distinct flora. 



Taking the genus acacia, which is very common in the interior, 

 it is interesting to note how very partial some of the species are in 

 regard to their selection of soils, and in this way serve as admirable 

 indicators of the quality of the land. A. pendula, A. Cunn., (myall or 

 boree), is always an indication of the black soil, its occurrence on a 



