98 Chapters in Modern Botany CHAP. 



perched plants depend on the rain and damp atmosphere, 

 for absorbing which the skin of the roots is often specially 

 adapted, forming a kind of sponge. And although the 

 roots do not come into contact with the soil, it seems that 

 in some cases they may absorb salts from the decaying 

 bark of their bearers, or from such debris as may gather 

 about the branches. 



From the great Cypress swamps of Florida, or the small 

 but better known surviving fragment of one of these which 

 surrounds the palace-citadel of Chapultepec, the favourite 

 morning ride of every visitor to the city of Mexico, the 

 traveller brings back a unique impression of mournful 

 picturesqueness. The sombre coniferous foliage is draped 

 with long silver-gray streamers, the " Spaniards' beards " 

 (Tillandsia usneoides), one of the most conspicuous and 

 widely distributed examples of the perching habit. This 

 has not even roots, but fastens itself to its bearer by means 

 of its long thread-like stems, the scales of which seem to 

 absorb the necessary supply of water. Aroids of the genus 

 Philodendron, often cultivated in our greenhouses, and 

 Orchids belonging to the genera Dendrobium, Oncidium, 

 Phagus, etc., are also good examples of epiphytes provided 

 with aerial roots, which absorb water -vapour from the 

 moist atmosphere of the tropical forest. Here indeed is 

 the solution of a mystery which has often puzzled the 

 botanist : how transpiration from the leaves could go on 

 without any apparent source of water-supply. A micro- 

 scopic section of the root, however, shows a tissue of 

 characteristically thickened cell-walls, which take up mois- 

 ture from the vapour-laden atmosphere during the coolness 

 of night. 



The best general account of Epiphytes is that given by 

 Gcebel in his valuable Pflanzenbiologische Schilderungen 

 (Part I., Marburg, 1889). With this Schimper's Epiphy- 



