48 Letters on the Diseases of Plants. 



In the second ease the death of the tree is usually slower, and bhe cause is 

 commonly more hidden from sight. The wood of the dead tree, however, on 

 being examined carefully, or compared with healthy wood of the same kind, 

 exhibits the peculiarities well known to timber merchants and carpenters 

 under the name of dry-rot. The diseased wood is softer and more brittle 

 than sound wood, and differs also in colour, and finally becomes punk and 

 falls to pieces. This deterioration is due to the presence among the fibres of 

 the wood of the hyphte or vegetative organs of a fungus whose fruit may 

 sometimes be seen either growing out from the bark in the form of "shelves" 

 or " brackets," or in the form of toad-stools near the base of the tree. 

 Strange as it may seem, the microscopic " roots," as we may almost call the 

 vegetative organs of these fungi, penetrate long distances into the solid wood 

 of the tree, where, by gradually absorbing and changing the substance of the 

 cells of the wood, they weaken it and give rise to the well-known appearance 

 of dry-rot. The death of the whole or part of the tree follows as a matter 

 of course. (See back trees in Fig. 59.) 



Both these conditions may occur in the same tree, and it is therefore well 

 to give as clear an idea as possible of the external appearance due to each of 

 these diseases. The illustration opposite (Fig. 59) gives a very good idea 

 indeed of the whole matter. The insect attacking the peach-trees represented 

 is the notorious cherry-tree borer, and is the larva of a night-flying moth, 

 while the trunks of the back trees are represented as attacked by both 

 Polyporus (bracket-fungus) and Agaricus (mushroom). The material for 

 this illustration I obtained through the kindness of Mr. Devlin, of Estella, 

 Wagga Wagga. 



Remedies. 



1. Trees dead or dying from either of these causes should be burnt. If 

 there is reason to attribute the death to dry-rot fungi, the stump and main 

 roots should also be destroyed by fire and the ground treated with quick- 

 lime. 



2. Keep the place free from rotting and decayed timber. Such only forms 

 a nidus, from which spring the spores of the dry-rot fungi. 



3. Where timber-rot is prevalent, take the precaution to disinfect with tar 

 the wounds on trees, either those caused accidentally or by pruning. In 

 pruning be careful to use sharp tools, and to use them skilfully, and cut off 

 the limbs close to the trunk or main branch that bears them, the idea being 

 to give the tree a good chance to heal the wound as rapidly as possible. 

 (See Fig, 22, p. 21.) 



4. Remove superfluous bark, and whitewash the trunk and main branches. 

 (See p. 27.) 



5. Where a wound fails to heal over, and becomes a sore, cut away the 

 wood as directed for Mai di Goma of citrus-trees. (See p. 29.) 



6. Look out that the drainage is good. This is a most important precaution 

 against timber-destroying fungi. Damp, ill-drained forest is their natural 

 home. 



7. As regards the remedies for borers, it is necessary to point out that 

 they are, for the most part, totally different to the preceding ones, directed, 

 as they are, against an insect instead of a fungus. It is when I observe 

 remedies for fungi being applied to trees suffering from borers, and vice versa, 

 that I realise how necessary it is to point out the possibility of being deceived 

 as to the nature of diseases through resemblances such as have been described 



