ARID PORTIONS OF SOUTH AUSTRALIA. 73 



rootlets which have been seen to occur on similarly placed superficial 

 laterals of several species in the Tucson, Arizona, region. 



The roots of perennials growing on the Copley Plain, and described 

 in the foregoing paragraph, are all either sharply vertical or as sharply 

 horizontal ia position. It is probable, from the large number of ob- 

 servations, that this is the usual condition. However, an exception 

 was found by a wash on the edge of the plain, where the soil is fairly 

 coarse and the bank is about 2 meters high. Here an undetermined 

 halophytic shrub of small stature had a root-system which was unlike 

 that above described. In this instance there was a brush of roots, 

 without the sharp differentiation into the vertical and horizontal 

 members as elsewhere observed. This condition is probably attributa- 

 ble to the fact that the soil at the place is relatively coarse, permitting 

 a deeper penetration of the rain and better conditions of aeration 

 than would more commonly be the case. 



Vegetation of the Low Hills and Slopes. 



The lower hills and slopes and the slopes of the higher hills are 

 usually well covered with a perennial vegetation. Although some of 

 it is of the halophytic type, it is largely composed of sclerophyllous 

 shrubs, fairly uniform in appearance and generally of a relatively 

 small size. The hill vegetation is so varied in species that it would 

 require a much closer study than the present one to describe it at all 

 accurately, as well as the aid of a large-scale contour map showing 

 the leading geological features. Such, unfortunately, appears to be 

 wanting. Certain leading characteristics, however, can be presented 

 as a preliminary study. Possibly the most striking single feature of 

 the hill perennial flora is the frequent segregation of species, so that a 

 relatively large area may be populated by a single one to the exclusion 

 of all others. This was noted again and again. Although there are 

 many species of perennial habit on the hills, it is probably true that the 

 most typical belong to two genera. Cassia and Eremophila. It will 

 therefore probably convey the right impression if the vegetation of 

 the hills was defined as the Cassior-Eremophila community. Following 

 are some of the most conspicuous species of the low hills and slopes: 



Eremophila brownii. Eucalyptus oleosa. Atriplex vesicarium. 



E. freelingii. Cassia eremophila. Bassia lanicuspis. 



E. oppositifolia (plate 8c). C. sturtii. Hakea leucoptera. 



E. latrobei. Myoporum platycarpum. Nicotiana suaveolens. 

 Zygophyllum fruticulosum. Acacia sentis. Petalostylis labicheoides. 

 Z. crenatum. A. aneura. Solanum iUipticum. 



Z. prismatothecum. Cheilanthes tenuifoliia. Menkea australis. 



Pholidia scoparia. Kochia planifoUa. Pimelea microcephala. 



Fusanus acuminatus. K. sedifolia. Triohinium incanum. 



F. spicatuB. Euchylsena tomentosa. Casuarina lepidophloia. 



