60 



PEACTICAL BOTANY 



covered with Japanese ivy furnish beautiful examples of leaf 

 mosaics on a large scale, and many of our common house plants 

 illustrate the same phenomenon. In any leaf mosaic many 

 of the leaves occupy a very different position from that which 

 they would have if borne on a vertical stem. 



FIG. 46. Poison ivy, a root climber 

 Reduced 



57. Obtaining better illumination 

 by climbing. While the "stemless" 

 plants and low mosaic formers uti- 

 lize light very advantageously by 

 the disposition of their leaves, many 

 plants get an increased light sup- 

 ply by climbing. On account of the 

 great height and dense growth of 

 tropical forests, climbing plants or lianas reach their greatest 

 development in those regions, often running hundreds of feet 

 to emerge at last into the blazing sunlight above the tree tops. 



FIG. 47. Twining stem of hop 



