30 



of the banana is injured sufficiently to allow the access of air to the- 

 broken cells beneath the epidermis an oxidation sets in that has the 

 effect of producing reddish and brownish colouration. 



The different species of banana, however, act somewhat differently 

 in this respect, and this may account for the fact that this reddish 

 colouration is less common and less marked on bananas from the 

 northern districts of New South Wales than on those from Queensland. 



The general appearance of the disease is that of one due to the 

 attacks of some vegetable parasite. 



In some cases it seemed as if the disease had started at a point on 

 the fruit where the latter had been chafed by rubbing against other 

 fruit in the same bunch ; still, in many cases the disease occurred in 

 places that bore no traces of chafing, and the only conclusion I could 

 arrive at from this part of the examination was the provisional one that 



Fig. 49. Advanced stage of the banana scab. The skin of the fruit is completely diseased, and 

 the pulp is worthless. The skin is everywhere grey, dry, and crackled. 



the malady was caused by a fungus having the power of attacking and 

 penetrating healthy epidermis. This conclusion cannot be accepted 

 without reserve until the disease has been produced on sound tissue 

 through contact with germinating spores. 



Sometimes the scab covers the greater portion of the surface of the 

 fruit. In such instances it is out of the question that friction could 

 injured so much of the surface. These cases add weight to the 

 evidence already accumulated in favour of some fungus being able to 

 work its own way into the skin of the sound banana. 



Some difficulties arise in searching for traces of the fungus causing 

 the disease. Pustules may be found scattered over the green or reddish 

 parts of the skin in the form of minute raised points. They are to be 

 found only on those parts manifestly suffering from the disease. 

 These pustules have nearly the same general colour as the area on 

 which they occur. Just previous to, or at the time of, rupture they 

 measure three to four hundred micromillimetres in diameter, some- 

 times even six hundred micromillimetres. 



If a recently ruptured pustule be cut away in such a manner that 

 little else is removed, and be then smashed in a very small amount of 

 water, spores will usually be found, though not in great numbers 



