71 



2. The disease is exceedingly common on trees that have yielded no 

 apparent insect cause. Where the fruit, leaves, &c., are so thoroughly 

 infested, it is hardly even conceivable that an insect cause could have 

 been overlooked by competent observers. 



3. The disease yields to treatment with Bordeaux mixture. This 

 points distinctly to the cause being a vegetable parasite. 



4. Fungus elements are found associated with the disease. Cultures 

 may be necessary for the satisfactory verification of this statement. 



All these items are in the nature of inferences, it is true, and no single 

 one of them can be taken, in the form stated above, as a proof of the 

 vegetable origin of the disease ; but taken together they seem to me 

 to form an almost overwhelming argument in favour of vegetable 

 origin. 



The following cultures were made in infusion of orange peel : 



1. Water culture of healthy epidermis of an orange attacked by 

 Melanose (?). After twenty-four hours there were only two growths. 

 These were from spores resembling those of Coniothecium and mani- 

 festly lying on the surface of the peel. The epidermis was shaved off 

 very thin at a place where there were no traces of the disease to be 

 seen. All the stomata, on examination with the microscope, proved 

 to be entirely free from discolouration. 



2. Water cultures were made from stomata just beginning to show 

 traces of the disease. These stomata were barely yellowed or decidedly 

 brown. In no case could any satisfactory traces of a parasite be seen 

 after twenty- four hours. If a vegetable parasite is present it must be in 

 a very attenuated form. Of interest in this connection is the fact 

 that in cultures of the well-developed scab the yeast-like conidia, 

 as they go on dividing, decrease in size until they are very small indeed. 

 Is it not possible that there is a generation of exceedingly minute 

 size ? Will this account for the difficulty in making out the parasite 

 at the time of the beginning of the attack ? 



3. Cultures of well-developed scab have yielded the results already 

 described and figured in this Gazette. The scab of orange gave very 

 little of the Coniothecium form, but the production of conidia was so 

 like that of the culture of the lemon scab that I could see no difference 

 in the two forms of conidia, except the more constant occurrence in 

 the latter of vacuoles. The same diminution in size occurred in each. 



MELANOSE (?) ON LEMONS. 



FKOM the same orchard that furnished the oranges upon which the 

 foregoing observations were made, some lemons were forwarded as 

 suffering from the same complaint as the oranges. 



In the case of the lemons it was not possible to show that the spots 

 originated at the stomata. Fungus elements were found among the 

 tissues of some of the scabs of the lemon corresponding with the Conoi- 

 thecium scabrum of McAlpine. The form found in the tissues as taken 

 from the dry scab and examined at once in water, consisted almost 



