Page:The Journal of Indian Botany.djvu/33

Rh 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:

It will be seen that except on the narrow stripe which is periodically 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 halophytes 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 accumulated 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.