547 



Dongas. — These are shallow depressions of varying size 

 a,nd extent which occur scattered over the plain. Except in 

 the smallest and most shallow, there is a considerably greater 

 -quantity of soil in them — a soil, too, which is much freer 

 from, limestone fragments. 



The dongas examined, which, however, were all com- 

 paratively close to the eastern border of the plain, bear a 

 v^egetation with trees or shrubs (pi. xxxii., fig. 1). The most 

 general were species of Acacia, especially A. aneura (mulga), 

 A. Oswaldii, A. tetragon ophf/Ua, with less often A. 

 Eandellmna. 



Other trees occurring we're Pittosporuin phillyraeoides, 

 Fusanus persicarius, and locally Casuarina lepidophloia. This 

 last was seen only in the largest depressions where there was 

 most soil. Eremophila Latrohei occurred rarely. Beneath 

 these trees the soil was quite bare in the smaller depressions, 

 but in the larger ones herbaceous plants (mostly annuals) 

 were present in some quantity. These were generally quite 

 -different from those on the general surface of the plain; 

 C ephaliptertim Drummondii, however, was usually present. 

 ■Stipa scahra was locally quite abundant, though at this season 

 it appeared dead. 



Other annuals found in these dongas were Salsola kali, 

 Lavatera pleheja, CoTivolvidus eruhescens, Lotus australis, 

 "var. pubescens, Helipterum ftorihundum, Nicotiana suaveo- 

 ■lenSy Calarcdriniu voluhilis, Pimelea simpler. 



In several of the dongras near the eastern margin of the 

 plain much of the undergrowth has been destroyed by rabbits, 

 ^hich have their burrows there. 



At the eastern margin of the Nullarbor Plain a certain 

 amount of change in vegetation is seen. More soil is pre- 

 sent and a richer vegetation develops. Small trees and shrubs 

 'Occur scattered over the surface, though often localized in a 

 peculiar way (pi. xxxii., fig. 2). Most of the shrubs found in the 

 "dongas grow in this situation, with the exception of Casuarina 

 ■lepidophloia . Tlie most abundant shrubs are Acacia aneura, 

 A. tetragonophylla , and Eremophila Latrohei, with Acacia 

 Mandelliana, A. Oswaldii, Pittosparum phillyraeoides, 

 Fusanus persicarius, and Eremophila oppositifolia, less fre- 

 quently. Here also the undergrowth is rather more luxuriant; 

 Kochia sedifolia, A triplex vesicarium, and others occur some- 

 what closer together. The annual flora resembles that of the 

 ■plains themselves, but certain perennial plants appear in this 

 zone, e.g., Solanum esuriale, S. coactiliferum, Sida corru- 

 •gatd. On disturbed ground near the village Galandrinia 

 polyandra and Euphorbia Drummon-dit are found in some 

 quantity. 



