186 



adhering to them. When these serial roots eventually reach 

 the ground they branch therein and rapidly develop a 

 wide-spreading root-system in the soil. If by this time 

 the death of the tree attacked has not been caused by the com- 

 petition of the fig's crown of foliage, the competition of the 

 fig roots in the soil now help in effecting this result, and the 

 fig with its own root-system established in the soil no longer 

 requires the help of its first support. Many epiphytic species of 

 Ficus are thus capable of destroying our forest trees, and it is 

 interesting to note as an historical fact that the famous Banyan 

 " in the Calcutta Botanic Gardens began life as an epiphyte on a 

 wild date-tree of which all trace has long disappeared."* This 

 tree is said to have been about 100 years old in 1886, with 232 

 supporting trunks developed from serial roots. The circumference 

 of its crown was then 857 feet, and it was growing vigorously. 



Although they are not competitors in the sense here ascribed 

 to the term, the fungi belonging to the genus Meliola deserve 

 mention here as injurious epiphytes. As has already been men- 

 tioned in Part IV above, these minute plants growing on the 

 surface of the leaves of trees and shrubs, and feeding on the sweet 

 juices excreted by insects cover the leaves with black incrusta- 

 tions which, by preventing the access of light to the green chloro- 

 phyll, are more or less injurious, see p. 133. 



Here also may be mentioned the Lichens which are so often 

 found growing on the stems and branches of trees. A luxuriant 

 growth of lichens is primarily an indication of a moist atmos- 

 phere and also frequently of very slow growth in the trees on 

 which they are found, for quick growth combined with the rapid 

 ex-foliation of the outer layers of bark prevent the establish- 

 ment of a vigorous growth of lichens. In so far as direct injury 

 "is concerned the latter are usually of very little importance, 

 their injurious action, being apparently confined to inter- 

 ference with the access of oxygen to the living tissues through 

 the lenticels. 



(b) Parasites. 



165. The most injurious plant 



parasites are undoubtedly to be found among the Fungi, of 

 which only a few typical examples can here be considered in 

 detail, viz. : 



(1) Phytophthora infestans. 



(2) Fomes annosus. 



(3) Trametes Pini. 



(4) Puccinia graminis. 



* Flora Simlensis by Colonel Sir Henry CoJlett, page 459. 



