253 



Only three annuals are included in the list, but at the end of a long dry- 

 season most of the annual species would disappear. The dry climbing stems of 

 Thysanotiis Patersonii, which is a geophyte, were quite common amongst the 

 stems of A. paludosum. 



Drainage channels and hollows in the A. paludosiini zone were colonized 

 by Arthrocnemmn halocnenioides, the lines of junction being very sharp (pi. 

 XX., fig. 3). 



Atriplex sHpitatiini community. 



Remains of the indigenous flora are scarce behind the level coastal plain. 

 Most of the inland area seen is entirely modified by farming, but near the head 

 of the Gulf is an area of red sandy soil that has not been ploughed. This is 

 colonized by a degenerate saltbush scrub, Atriplex stipitatum being the most 

 abundant plant present. This species forms low rounded bushes about 50 cms. 

 in diameter with an open spreading habit. Other plants present were : — 

 Lomandra effusa Enchylacna tomentosa 



Fusanus acumhiatus Acacia sp. (Osivaldii ?) 



The list is certainly far from complete, but the combined efifects of rabbits, 

 heavy grazing, angl the season of the year made it impossible to collect specimens 

 suitable for identification. The interest in the area, however, lies in the develop- 

 ment of the saltbush A. stipitatum. 



The soil is of a very different type (sample No. 10). It is highly silicious, 

 with only 9 per cent, of lime and 2'3 per cent, of organic matter. The soil was 

 air dry when collected, and the moisture content of 2 5 per cent, indicates a 

 very poor water retaining capacity. The most interesting difference, however, 

 is that sodium chloride is present as a mere trace, 02 per cent. 



DISCUSSION. 

 From the foregoing it is clear that the zonation noticed in the vegetation 

 may be correlated with certain edaphic features of the environment. First, the 

 range of water content of the different plant habitats may be expressed as 

 follows : — 



Arthrocnemum arhuscula . . . . . . 20-50 per cent. 



A. halocnemoides . . . . . . . . 5-20 ,, ,, 



Atriplex paludosum . . . . . . . . 5'0-7'5 „ „ 



A. stipitatum . . . . . . . . . . 25 „ ,, 



Further, if the salt content be considered, whether total salts or sodium 

 chloride, a similar division of the soil analyses may be made : — 



Total Salts. NaCl. 



Arthrocnemum arhuscula .. 16'9-17'5 p.c. 1570-16'71 p.c. 

 A. halocnemoides .. .. 2 9- 4 9 p.c. 2 30- 3'77 p.c. 



Atriplex paludosum .. .. 16- 2 8 p.c. 78- 162 p.c' 



A. stipitatum .. .. .. 03 p.c. 2 p.c. 



From the above figures one can obtain a ratio expressing the proportion of 

 salts to water in the soil at the time of our visit, i.e., one can gain some idea of 

 the density of the soil solution at that time of the year. This ratio is given below, 

 taking total salts in the wet soil as unity, and giving the amount of water pre- 

 sent in the soil as collected as a ratio of this figure. The results are as follows : — 

 Arthrocnemum arhuscula . . . . . . . . 1 : 3 ■8-40 



A. halocnemoides . . . . . . . . . . 1 : 43 



Atriplex paludosum . . . . . . . . . . 1 : 30-3'3 



A. stipitatum . . . . . . . . . . ..1:83 



It follows that A. paludosum has in contact with its roots a solution that 

 is actually denser than that in which the salt marsh plants are growing. But 

 this solution was not being absorbed by the roots in March, for, as noted above. 



