The plant which performs this strange feat is the Tillandsia usneoides, indigenous to tropical America, and generally known as ‘Spanish Moss’. Its peculiarity is that it grows and flourishes without taking from its support any material whatsoever for the building up of its substance. Its natural habitat is the dry bark of virgin forest trees. Since civilization invaded its home it has acquired the habit of growing even on telegraph wires, which has given it the popular name of ‘telegraph tresses’. Chemical analysis of this plant shows the presence of an average of 17 per cent iron, 36 per cent silicic acid and 1·65 per cent phosphoric acid. This applies to samples taken from districts where the rainwater – the only source from which the plant could extract these substances in physical form – contains at most 1·65 per cent iron, 0·01 per cent silicic acid and no phosphoric acid at all.