466 CITRUS FRUITS AND THEIR CULTURE. 



ated with the life functions of the cells. These are 

 grouped under the general name of Physiological Dis- 

 eases. 



FUNGUS DISEASES. 



Foot-rot,, Gum Disease, Mal-di-goma. So far as 

 known, this disease occurs in nearly every citrus dis- 

 trict in the world and none of our American centers 

 are free from it entirely. Its history in Europe extends 

 back to about 1845 and it worked destruction in the 

 groves of the Azores some years previous to that time, 

 and, in fact, seems to have been first noted there. In 

 Florida, it has been responsible for the disappearance 

 of many of the old sweet seedling groves and the discontin- 

 uance of the use of the sweet orange as a stock, as noted 

 in the chapter on stocks. 



Foot-rot is clearly marked and not likely to be con- 

 founded with any other disease.. It is confined to the 

 crown and main roots of the tree, extending a foot or 

 so above the ground and downward along the roots. Its 

 presence is first indicated by an exudation of gum, which 

 forms in drops on the bark covering the diseased spot. 

 Further examination at this time reveals a brownish 

 coloration of the outer cortex and a decayed condition 

 of the inner. The affected areas emit a fetid odor simi- 

 lar to that from a decaying orange. All plants, when 

 attacked by a disease, strive to overcome it, and this the 

 orange tries to do by cutting off the affected portion by 

 a wall of new tissues similar to that formed around an 

 ordinary wound. Following this, the bark covering the 

 spot dries up, breaks away from the adjoining parts, and 

 drops off. The wood is then found to be decayed for a 

 short distance beneath. 



