W. RUSHTON 



367 



somewhat fibrous strands intermingled with them, the walls of this 

 open tissue being of cellulose, similar to that of closed tissue. 



Dusting spores on the uninjured skin, laying on mycelium or 

 putting on mycelium together with gelatine medium, it was found 

 impossible to induce the fungus to attack the orange so long as the 

 cuticle of the skin was undamaged, but if the cuticle was pierced with 

 a sterilised needle or small pieces of it were removed with a razor, 

 then the fungus soon attacked the underlying parts of the skin sur- 

 rounding the oil glands or between the oil glands and the cuticle. 



Cuticle 



N Yellow 



/ tissue 



X, White 

 ^ tissue 



^ Irregular 



Diagram of section of orange skin. 



strand 



The first symptom of attack is a brown coloration in the region 

 of infection, which soon spreads in all directions under the cuticle. 



Later on the white mycelium of the Penicillium appears and 

 follows in the wake of the coloured tissue, and as the discoloration of 

 the tissues continues so the Penicillium spreads at the same rate. 



On examining this brown tissue no fungal hyphae could be found 

 and it appears that when the fungus gains an entrance into a host 

 it pours out an enzyme which acts on the tissues in the neighbourhood 

 causing them to change colour. This change occurs first in the cell 

 contents and later the cell walls break down. 



