10 



THE MONTHLY BULLETIN. 



ing out from this cut, killing the hark; this was followed hy considerable 

 gumming. After the diseased area had worked half way around the 

 trunk the leaves began to turn yellow and a heavy bloom appeared. 

 Just before the freeze the tree had reached the stage in which the fruit 

 was failing to develop, and was turning yellow when about half grown. 

 The tree at this time was almost girdled and had the appearance of a 

 typical case which had gone too far to warrant any course being taken, 

 except to blast it out and replant with a young tree. 



The proof of the infection and investigation into the nature of the 

 disease was carried further by secondary inoculations and cultures. 

 Cultures made from the bark of this, and other typical cases of gum- 



FiG. 3. — Lemon tree showing area of 

 dead bark outlined by inner dark line 

 ■ — outer line showing where cutting 

 out should be done. (Original.) 



mosis developed the brown rot fungus, Pythiacystis citrophtliora; sec- 

 ondary inoculations made from these cultures on healthy trees in turn 

 developed the typical lemon gum, and again the fungus was isolated in 

 culture from the secondary inoculations. The fungus being identified, 

 lemons infected with brown rot were placed against healthy trees and 

 gum disease was produced on the trunks, while the reverse experiment 

 of infecting sound lemons by laying them against diseased bark 

 further proved the cause to be due to this fungus. This series of 

 inoculations, cultures, and various experiments carried out by Profes- 

 sor Fawcett have clearly demonstrated that, contrary to previous be- 

 liefs, the common lemon gum disease is infectious and caused by the 

 brown rot fungus alone. 



