Pathogenicity of the Chestnut Bark Disease 59 



A new series of tests with sodium hydroxide, sodium car- 

 bonate and lithium carbonate proved the last salt to be more than 

 twice as toxic to the fungus as the sodium salts. The solutions 

 were injected through the roots of chestnut trees growing in the 

 greenhouse. It was found that the trees showed individuality 

 as to the percentage of the salt they would readily absorb. This 

 possibly is due to the difference in sap density of the trees. In 

 all of this work the solutions were made up very carefully by 

 titrating. As nearly as could be determined by the hydrometer 

 the density of the solution imitated that of the cell sap. 



Injection experiments were conducted during the summer 

 of 1912 at Emilie and Martic Forge, Pa. Here .2, .25, and .33 

 per cent lithium carbonate, 1 per cent formaldehyde and 1 per- 

 cent tannic acid solutions were used. These were injected into 

 trees 5 to 7 years old showing cankers at their base. Solutions 

 of strength sufficient to inhibit the growth of the fungus would 

 also impair the vitality of the tree, often causing death. The 

 heavy metals are of little value in tree medication. No success- 

 ful method of either killing or checking the growth of the fungus 

 was found. 



Parasitic and Saprophytic Growth of the Chestnut Bark Disease 

 and Similar Fungi. 



In this paper the fungus will be called a parasite when it is 

 found growing in cells of the host tree which are alive, that is. 

 cells which contain protoplasm capable of responding to stimu- 

 lation. It will be called a saprophyte when found in cells in which 

 there is no living protoplasm. Generally speaking, the living 

 cells in the trunk, branches and twigs of a tree are confined to 

 the cambium and to the zones of cells lying on either side of this 

 sheath. Most of the cells of the bark and wood of a tree are 

 dead. The fungus may be found growing as a saprophyte on a 

 living, healthy tree when it is growing in the thick bark at the 

 base of the tree ; when it reaches the cambium layer and grows 

 there it is a parasite. 



The active parasitism of the chestnut bark disease has been 

 verified by several thousand successful inoculations. Lesions may 

 occur on any or all parts of a tree above ground and may girdle 

 the tree at any point. The roots are rarely, if ever, attacked. 

 Microtome sections, permanent slides and photomicrographs were 

 made showing the hyphae of the fungus in the vessels and wood 

 parenchyma of the sixth annual ring from the periphery. 



In July, 1912, the chestnut trees, both young and old, were 



