THE (ECOLOGY OF SPINIFEX SQUAEEOSUS L. 23 



Other workers have observed the same thing, that water does not 

 rise by capillarity in sand ; the explanation probably being that there 

 are no capillary tubes formed as in a fine grained clay. The dampness 

 of the sand just below the surface is then not due to a rise from below. 

 The only other source of water is from above, as rain or dew ; 

 and it seems clear that the water in sand even by the sea is not salt 

 water drawn up from below nor even brackish but quite fresh rain 

 water, preserved by the inability of the sand to draw it up to the 

 surface when it would quickly be dried by the sun. 



To test this point, we dug pits in the sand till free water was 



obtained, the depth varied from 2 to 6 feet. The salt in the water 



was estimated by standard silver nitrate solution. Samples were 



taken from different parts of the beach with the following results : — ■ 



Plant growing Salt. 



Cyperus arenareus ... ... ...0'2 — 0'5 per cent. 



Do. with Launsea pinnatifida ... 0*25 ,, 



Hydrophylax maritima ... ... 0*35 ,, 



Spinifex squarrosus ... 0"85 ,, 



(No plants) near sea ... ... 6'3 ,, 



It will be seen that except on the narrow stripe which is periodi- 

 cally inundated by the sea, the salt-content is very low. It should be 

 noted that the water obtained at, say, 3 feet is not all water which has 

 sunk down from above but some naturally free at that depth. The 

 sinking is clearly seen when the pit is dug. It seems therefore that 

 Spinifex squarrosus and other strand-formation species are not halo- 

 phytes at all as suggested by Schimper (3) Warming at one time, (4) 

 and others, but rather xerophytic psammophytes, depending for their 

 water-supply on the rain-water -and dew retained by the sand. The 

 former, it may be noted, though it sinks through the surface layers 

 almost or quickly as it falls, would not pass through the lower layers 

 quickly, for the sand on these low beaches must be saturated at no 

 great depth by the sea-water which has filtered through. As regards 

 dew we have noticed, during the hot weather, in the early morning 

 before sunrise, distinct deposits of dew on the seaward face of every 

 little lump of sand, e.g., the sides of a foot-print and round plants, as 

 if deposited when a slow moving moisture-laden breeze passing over 

 the cooling sand was delayed by the small obstruction. The accu- 

 mulated affect of this dew, slight as it is, would keep the sand below 

 the surface damp and supply fresh water to plants whose root-hairs 

 are near the surface. 



fectly justifiable to draw conclusions from experiments with definite volumes 

 enclosed in non-porous pipes. 



