1 June, 1902.] QUEENSLAND AGRICULTURAL JOURNAL. 481. 
Vegetable Pathology. 
REPORTED DISEASE IN MARYBOROUGH ORANGES. 
Report sy H. Tryon, Enromonoaist anp VEGETABLE PATHOLOGIST, 
DEPARTMENT OF AGRICULTURE. 
iJ 
Brisbane, 12th May, 1902. 
Srr,—I have the honour, by way of supplement to my communication of 
Sth instant, to report on the condition of two cases of Maryborough oranges 
received since (on the 9th May) at the offices of the Department, and forming 
part of a return consignment. 
* * * * * 
understood to have been already “condemned” in New South Wales on the 
ground that the fruit that it comprised was affected by ‘‘ Melanose,”’ as certified 
to by Mr. Inspector J. Martin, Inspector, Department of Mines and Agricul- 
ture, New South Wales (vide certificates 83rd May and 5th May). 
This fruit to which reference is made as above, I find to exhibit con- 
spicuously (in addition to dead scale-insects of more than one kind) skin 
injuries and blemishes, as follows :— 
1. Injured from Hydrocyanic Acid Gas.—The oranges affected by the 
cause specified manifest reddish-brown blotches and patches that merge at 
their boundaries with the generai surface colour, this being due to the fact 
that—as the result of chemical action—the chloroplasts of the cells of the 
superficial tissue have become disorganised, resolving themselves into brown 
particles and discharged brown colour, and the cells themselves killed. This 
injury, that is exhibited by a considerable portion of the contents of the cases, 
has probably arisen from the fact that the fruit—as ascertained—was green or 
partly green, at the time of treatment at Maryborough, in the ‘“ fumigation 
chamber.” 
2. Acarus Injury (? “ Melanose,” Cobb ; “ False Melanose,” McAlpine).— 
This injury, that in my opinion is caused by an Acarus belonging to the genus 
Brevipalpus (Rhapignathide), provisionally named R. citriperda, takes the form 
of linear markings, spots, blotches, and patches of very irregular outline or 
direction ; the former always well defined externally. These, except when 
their dimensions are considerable, as is commonly the case, when they are 
light-brown with often dark-brown narrow margins, are blackish-brown 
coloured. In the latter event also, the surface of the fruit embraced by 
them is irregularly tesselated by the presence of minute cracks. In some 
cases these larger markings are evidently formed by coalescence of mere 
specks or other small markings, and generally reproduce the form taken 
by water that has spread over an oiled surface—the appearance exhibited 
being such often as to recall to mind the idea of an archipelago. These 
markings of such varied size and form present the following microscopical 
features. In their initial condition there merely exists, in connection with 
them, a darkening of the entire contents of the cells of the epidermis, groups 
of these cells becoming uniformly dark-brown. These cells, moreover, may be 
covered externally with a special evenly distributed substance, that appears to 
have solidified after having spread or flowed over them. This is of fe nature 
of a resin, and dissolves in boiling potash, after the manner of that body. The 
layer of cellular tissue covered by this resinous matter, and with which it is in 
close union, has died and has become fissued—as already described—after the 
manner of mud in drying. When a portion of it is removed and freed from the 
imprisoned air that it contains, and otherwise suitably prepared, it may display 
the presence of mycelial-fungus threads that seem to be here and there directly 
