THE DISEASES OF PLANTS. 303 



roots are planted in, and feed on, the soil : all it requires 

 of the tree which it embraces, is support. Yet these 

 plants, as you observe, are frequently prejudicial. I have 

 seen trees whose branches have been so enveloped, and 

 strangled, as it were, with creepers, that scarcely any room 

 was left for its own proper foliage ; and the growth of the 

 tree was consideraly impeded. 



But to return to our parasites. The Rhizomorpha is a 

 false internal parasite, which attacks wood ; and, though 

 it does not feed upon its juices, the mere growth of the 

 plant proves fatal to it, disorganising its parts, and redu- 

 cing the wood to a sort of vegetable mould. This mala- 

 dy seldom occurs but in very aged trees. 



Emily. We, artificial beings, whose aim is to have 

 plenty of sound timber for building, consider this as a 

 dreadful malady ; but, in the course of nature, it may, per- 

 haps, simply be a means employed to reduce old or dead 

 trees, to the state in which they are fitted to return again 

 into the vegetable system, for this mould must afford rich 

 food for other vegetables. 



Mrs. B. In natural forests, where the hand of man 

 does not interfere to turn the timber to his own account, 

 it is certainly desirable that Nature should devise some 

 means of hastening the decomposition of wood, a sub- 

 stance so hard and compact that it would require a great 

 length of time to effect it by the usual process of decay. 

 In this operation, the Rhizomorpha is aided by a tribe of 

 insects, which take up their abode in the cracks and crev- 

 ices, it has made in the wood. 



Caroline. The Misletoe is, I suppose, a true parasite ; 

 for it derives its nourishment from the tree to which it is 

 attached. 



Mrs. B. The seed of the misletoe fastens itself to the 

 tree by means of a glutinous substance with which it is 

 covered. The radicle of this seed shoots out in a man- 

 ner different from that of any other plant : being too fee- 

 ble, on its first entrance into life, to penetrate so hard a 

 soil as wood, it shoots out in some other direction. 



1633. What is ivy and hoW does it injure trees'? 1634. What is 

 said of the Rhizomorpha'? 1635. How does Emily think it may be 

 serviceable in natural forests'? 1636. How is the Rhizomorpha aided 

 in producing the decomposition'? 1637. How is the seed of the mis- 

 letoe fastened to the tree, and what is said of its germination! 



