51 



iron oxide (turf ashes rich in iron), may perhaps act indirectly by check- 

 ing the formation of nitric, acid. 



From our present knowledge it seems advisable to keep soils which 

 experience has shown to foster potato scab well aerated by means of re- 

 peated harrowing. 



GUM DISEASE OR FOOT ROT OF THE ORANGE. 

 I. General Observations. 



For a number of years past the orange trees in Florida have suffered 

 from the attacks of this malady, and for the purpose of bringing to- 

 gether some of the facts in the case, as well as to awaken a deeper 

 interest in the matter, the following paper has been prepared: 



Gum disease, or "foot-rot," as the disease is commonly called in Flor- 

 ida, is not peculiar to the United States; but has long been known 

 in southern Europe, and the loss it has there occasioned to the lemon 

 and orange groves is estimated at many millions of dollars. An Ital- 

 ian writer, referring to the injury it has occasioned in one district in his 

 country, says : 



The damage already done may be estimated at not less than 10,000,000 lire ($2,000,- 

 000), in (act so extensive have its ravages become through the kingdom, that it is now 

 looked upon as a national calamity. 



The disease is supposed to have originated something over fifty years 

 ago in one of the Azores Islands, where it reached its maximum in 1840, 

 destroying in one year one-fourth of the orange trees on the island of 

 St. Miguel. According to Fougue ' it appeared in Portugal in 1845, and 

 occasioned the greatest injury there from 1858 to 1861. Opinions differ as 

 to the exact date it appeared in Florida. Judging from the reports of cor- 

 respondents, however, we conclude that it has been known in the State 

 for twelve or fifteen years. From statements made by Dr. A. II. Curtis 2 

 it appears that the "bad cases" are found at points on both the eastern 

 and western coast, as well as in the interior, but whether it was intro- 

 duced from Europe is not certainly known. 



II. External Characters ok the Disease. 



The disease, as a rule, is first manifested by the appearance of a 

 gummy effusion which appears, principally in the spring and autumn, 

 on the trunk of the trees close to the ground, or directly upon the root. 

 Even before there are any outward signs of diminished health, small 

 drops of gum appear on the bark of the trunk ; these increase in size and 

 number, and the bark appears to melt away or become honeycombed; 

 finally the gum liquefies, assumes a muddy brownish color and a disagree- 



1 Revue des deux Mondes. 



2 Bulletin No. 2, Florida Agricultural Experiment Station. 



