IDS 



The Salicornias and Suacda occupy the ])laces most exposed to spray. Else- 

 where Nitraria is the most important plant, often forming almost a thicket, over 

 the hushes of which Tetragonia and linchylaena scramhle. 



III. AtDiual Community. 



The plant covering growing upon the plateau of Middle Pearson Island 

 is of a type not seen elsewhere in the group (pi. ix.,' fig. 1 ). The main plants 

 observed were : — 



Lcp'idium foliosum Scnccio laiitiis 



Apiiim prostration 



Of these only the Lcpidiiiin was living in January. Occasional c]unii)s of 

 Enchylacna, the only perennial noted, occurred over the area. 



This plateau rises steeply at the western side to the granite summit, the 

 junction being a fan of talus from the tors above (pi. ix., fig. 1). At the 

 junction of fan and plateau there is a belt of Atriplex cincrcum noted above as 

 a constituent of the travertine flora. The vegetation of the fan belongs, of 

 course, to the mixed shrub community on granite rubble. Olcaria r amnio sa 

 predominating. 



It is very noticeable that the Olcaria does not colonize the travertine, though 

 it is found growing in clefts in granite exposures on either side of the plateaux. 



Communities influenced by Blown Sand. 

 Littoral. 



The only littoral plant on Pearson Island is Atriplc.v cincrcum, which grows 

 in a small patch at the north-west corner of the landing place (pi. viii., fig. 1). 

 The habitat is one in which Atriplc.v cincrcum ^'^ commonly occvtrs on the main- 

 land, but the habit is unusual. The plant grows creeping or semi-prostrate, 

 and so accumulates blown sand about itself through which it grows, forming 

 mounds 2 to 3 feet high and 4 to 6 feet in diameter. 



The other portions of the coast are unsuitable to the growth of flowering 

 plants, being either boulders or platforms of bare granite often of great extent. 



Blozvn Sand on Granite Rubble. 

 Behind the area mentioned above there is a trough in the granite extending 

 inland in which wind-borne sand mingles with the rubble. Atriplc.v cincrcum 

 !s replaced by Frankcnia pauciflora, which also holds the sands, forming low 

 mounds a foot or more in diameter ; a similar growth form of this plant was 

 observed on Franklin Island. Other plants are those of open communities 

 influenced by sea spray, except Lavatcra plcbcja, which was seen nowhere else 

 on the islands. 



DISCUSSION. 

 Plant Succession. 

 On so small an area climatic differences are not very marked, though it is 

 probably quite justifiable to regard the rubble plains and slopes at the foot of 

 the hills as more arid than the hills themselves. In atmospheric humidity, 

 intensity of insolation and temperature, if not in actual rainfall, the plains have 

 a more xerophytic climate than the hills. It is convenient to group the suc- 

 cession seen on Pearson Islands into three series. The plains bear a "saltbush" 

 ilora. that of the hills falls into a Casuarina woodland and a shrub series cul- 

 minating in Melaleuca parviflora scrub, and the flora on travertine limestone is 

 the third. 



(") Osborn, T. G. B., Brit. Associi. Report, Austr., 1914, p. 505. 



