With Spinifex squarrosus no tubular sheath is formed, for the secretion does not cause the sand particles to adhere. It appears to act rather as a lubricant or perhaps as a resisting layer to protect the piliferous layer from damage by sharp grains of sand. Spinifex is not related closely to any of the grasses noted by Price as possessing the mucilage layer. The genus consists of only four species, occurring on sandy shores of India, Malaya and N. Australia.
The Water-supply.
Every one knows that sand a very few inches below the surface is damp, as also is any ordinary soil. With ordinary clay or loamy soil this is usually taken to be due to an upward movement from low levels of water drawn up by capillarity through the fine cracks developed by the drying of the soil. This water being continually dried at the surface of the ground. There may be a slow upward movement of water also through sand ; but it is very slow. This was determined by us both in the laboratory and in the sand of the beach. In the laboratory two wide glass tubes were filled with dry sand, the lower end closed with muslin and the tubes supported with their lower ends, one in fresh water, the other in salt water. At first the rise of water as shown by the darkening in colour of the sand was rapid, but after the first day the rate fell off and after seven days the level was practically stationary at 24 cms; a slow rise went on for several days till it reached 30 cms. Then no further rise was noted. There was no appreciable difference between the two tubes. The experiment was continued for 4½ months without any change in the level of the dampness being seen. It came to an end with the rotting of the muslin holding in the sand.
In another series of experiments 8-inch drain pipes were sunk in sand in an enclosed space but open to the air. The pipes were 36 inches long. They were filled with dry sand, and some left open, others closed at the top. No appreciable rise of water could be detected after periods of three to six weeks except in one case where the sand had a musty smell and was slightly more damp below than above, pointing to a rise of water from below. Heavy rain had fallen and the sand outside had been saturated, so that the water might have come up as much by hydrostatic pressure as by capillarity.[1]
- ↑ The use of pipes in this way has been objected to by Olsson-Seffer (1) on the ground that no lateral movement of the air enclosed in the pipe is possible as would, he considers, occur in nature, and that the free movement of the water would be prejudiced thereby. But a little consideration would show that in a homogeneous medium of practically limitless extent (as the sands of the seashore) there can be no balance of lateral air-movement inwards or outwards from any imagined volume, and that it is therefore per-
