185 



supporting them more or less interferes with the descent of food 

 materials from the leaves in the tissues of the cortex and conse- 

 quently with the nourishment and growth of the cambium. The 

 latter may be thus killed in places and the stems or branches 

 become deformed and irregular, often assuming a corkscrew 

 shape owing to the growth in thickness taking place in a spiral 

 direction. It is, indeed, not uncommon to find dead stems which 

 have been effectually girdled by such climbers. 



164. This brings us to a considera- Epiphytes, 

 tion of the effect of so-called epiphytes on other plants. The 

 student must be careful not to confuse the term epiphyte with 

 that of parasite. An epiphyte is a plant which grows on 

 another plant, the term having reference merely to position 

 and thus serving to distinguish plants which grow on other 

 plants, from those which grow inside other plants (endo- 

 phytes), or on the earth (terrestrial), or in the water (aquatic). The 

 word parasite, on the other hand, refers essentially to the manner 

 in which the plant obtains its food, and an epiphyte in conse- 

 quence may or may not be also a parasite. We often see a 

 young Banyan (Ficus bengalensis), or Pipal (Ficus religiosa), 

 growing on the top of a large Mango or other tree. Year by 

 year the fig grows bigger and, as its dense crown of foliage 

 develops, it shades the Mango leaves more and more from the 

 sunlight. The Mango then begins to languish, and ultimately 

 dies. After several years an enormous fig tree alone is to be 

 found on the spot and no sign remains of the Mango on whose 

 branches it first started life. If we carefully watch the develop- 

 ment of such a fig we find that the young plant sends out its 

 so-called serial roots which rapidly spread downwards in all 

 directions along the branches and stem of the tree attacked 

 towards the soil. These become woody and frequently become 

 grafted together at points where they come in contact with 

 one another, thus forming a tightly-fitting, latticed, woody 

 mantle over the attacked stems. These roots also produce from 

 their under-surface small absorption-roots which, being nega- 

 tively heliotropic and positively hydrotropic, cling tightly to 

 the bark and penetrate into its dark cracks and fissures where 

 moisture and small quantities of dust and humus accumulate. 

 The latticed roots themselves also provide lodgment places for 

 dust and organic debris, and from this alone do such epiphytic 

 roots derive their nourishment, for they do not penetrate the 

 living tissues of the stem on which they grow. If such roots are 

 torn away from the stem enveloped by them, it is surprising what 

 a large quantity of dust and earthy matter may often be found 



