Letters on the Diseases of Plants. 29 



show that in at least one case of apparent Mai di Ooma, forwarded to me 

 at my special request, a fungus occurred in the diseased bark. The nature 

 of the case is well shown in the engravings and their subjoined explanations. 



Remedies. 



1. Cut away the diseased bark with sharp tools. Cut well into the wood 

 and remove every particle of diseased-looking bark. It is better to cut away 

 too much than too little. Burn the cuttings, and smear the cut surface over 

 with grafting wax. 



2. Eemove the earth from near the base of the tree and apply two or three 

 pounds of slaked lime. 



8. Secure good drainage. 



4. Avoid organic nitrogenous manures, such as dried blood and rich stable 

 manure. 



5. "Whitewash the trunks with a spraying machine, or with a brush. 



3. Verrucosis. 



This is a disease that affects lemons particularly, giving rise on the fruit to 

 unsightly warts of a light brown colour which are particularly noticeable on 

 the lemons when they are green. The disease causes many young lemons to 

 drop off, and it so deforms many others as to cause them to be comparatively 

 worthless. The disease is of fungous origin, and is said to yield to systematic 

 treatment with Bordeaux mixture. For specific directions the reader is 

 referred to the remedies given under " Melanose," p. 27. 



4. Die-back. 



This disease appears to be somewhat uncommon in this country, but cases 

 have been referred to me that appeared to be no other than cases of dieback. 

 There was the same abundance of small foliage of unnatural colour, and so 

 forth, but the matter mast remain unreported upon until I obtain further 

 information, to which perhaps some of our orchardists may assist me. 



5. Black Spot of the Orange. 



This disease is one that is very prevalent in some of the orange orchards 

 near Sydney. Like Melanose it lowers the market value of the fruit. It also 

 makes it impossible to keep the fruit in store, as the spotted oranges soon 

 become rotten. The appearance of Black Spot on oranges is well shown in the 

 illustration on the following page, (Fig. 34.) It will be seen that the round 

 sunken spots are large and conspicuous, and seriously mar the appearance 

 of the fruit. The central part of each spot becomes greyish or whitish when 

 the fungus causing the disease is mature, at which time several minute dark 

 pustules appear in each spot. These pustules give rise to a multitude of 

 spores of the form shown in the wood-cut below. These spores arise after 

 the manner of those of the genus Gloeosporium. It is therefore possible 

 that the Australian form is the Golletotrichum adustum of Ellis. 



