32 



tors have not yet determined the whys and the wherefores. 



Some individuals are of the opinion that it is caused 

 by the punctures of insects the orange mite through the 

 outer rind into the oil cells, thereby causing the oil to 

 ooze out and spread over the rind, which oxidizes and pro- 

 duces the stain as we find it. Others think it is caused 

 wholly by the excretions of microscopic insects ; while 

 others still, maintain that it is natural rust of a fungoid 

 character. Our investigations, which have been rather 

 extensive and thorough, leads to the belief that the rust is 

 the result of both the workings of insects and a fungus. 



It is noticeable that the rust seldom covers the entire 

 rind. Sometimes one side only is stained ; sometimes a ring 

 extending around the middle, and sometimes only a spot 

 or specks will appear. When in the way of observation, 

 it has been found that the orange is green and smooth up 

 to half its natural size. Then a smooth, light colored sub- 

 stance would appear in places, or over a portion of the surf- 

 ace of the fruit, seeming like the light glary trail left by a 

 snail. Examination of portions of the rind at this time 

 with the microscope, has revealed the presence of minute 

 insects, and also the presence of the ordinary orange scale. 

 The light glary substance was found evenly spread over 

 portions of the surface, corresponding to the rusty surface, 

 which subsequently appeared. Subsequent examinations 

 with the microscope revealed minute fungus spread over 

 the entire surface of those bands and patches covered by 

 the glary substance. These occurrences leads to the belief 

 that the light glary substance seen on the rind was & secre- 

 tion of the insects, which remains and forms a fit lodging 

 place for the spores of fungi to develop. 



What confirms us more strongly in the belief that in- 



