202 



on the limestone, so that the upper-surface becomes etched by 

 their growtli and finally eaten througb. 



Two annual grasses grow in the sand-filled cracks of the 

 limestone pavements. They are Danthonia setacea and 

 Calamagrostis filifonnis, of which the former is most 

 abundant. At low levels near the sea M esemhryaTithemuin 

 australe and Tetragonia implexiconia also occur; the latter was 

 only seen along cliff edges, over which it scrambled. 



Where the pavements are covered by sand, Nitraria 

 S cho eh eri develoips a more or less extensive mound owing to 

 its growth habit (6) (pi. ix., fig. 1). With it Olearia axillaris, 

 and occasionally Stijxi tereti folia, become associated. These 

 plants represent a colonization of the pavement by the flora 

 of unstable sand, owing to the Nitraria; they are not typical 

 of the flora of the limestone pavement as such. 



Frankenia fruticulosa is certainly the character plant of 

 this association. It gives a most characteristic appearance to 

 the areas, which can be distinguished from a distance by their 

 light-grey colour (pi. xi., fig. 1). The stability of the associa- 

 tion is limited by the existence of the limestone. As this is 

 broken up by the solvent action of the roots or rain water, 

 the proportion of sand exposed becomes greater, leading to 

 an increase in the number of annuals, and also such sand- 

 collecting bushes as Nitraria and Olearia. Ultimately, there- 

 fore, the travertine pavement flora is replaced by an open 

 shrubland passing through a phase in which tlie proportion 

 of grasses is greatly increased. Such a, transition was noticed 

 on the roof of Western Franklin in a ridge of sand with 

 limestone rubble, bearing old plants of Frankenia fruticidosa 

 and much Danthonia penicillata, which is a perennial. 



(Hi.) Open association on loose sand. — At present about 

 half the roof area is occupied by an open association in which 

 the most prominent plants are Salsola kali, Lepidium foliosum, 

 and tussocks of Stipa teretifolia, tlie only perennial plant con- 

 stantly present (pi. ix., fig. 2). With these also occur Broiniis 

 arenarius, Siloxerus tomentosus, Vittadinia australis, etc. 

 Such areas are literally honeycombed by the burrows of mutton 

 birds or penguins, so much so that they are unpleasant to 

 walk across, as the ground constantly caves in under-foot. The 

 soil is, therefore, constantly disturbed, and large areas are 

 bare, though annuals probably occur in the winter months. 

 As our visit was paid in January no list of this therophyte 

 flora could be made ; from the fruits collected under bushes 

 it was clear that an introduced Hordeum occurred, and also 

 Daucus brachiatus. Nitraria Schoeheri plays a prominent part 

 in this association in some places (pi. viii., fig. 2) ; it develops 



~ (6) Cannon, W. A., I.e., p. 70. 



