DISEASES OF LIME AND OTHER CITRUS TREES 223 



that the defect is one of appearance only. It was found that 

 similar spots could be artificially caused by scratching the rind. 

 A convincing explanation of this condition, which is trouble- 

 some on lemons in California, was supplied by H. S. Fawcett 

 to the effect that it is caused by the action on the tissues of 

 drops of the essential oil of the fruit, when this is liberated by a 

 scratch or a slight bruise. It is found that the spots are only 

 produced when the fruits are moist with rain or dew, and that the 

 restriction of picking to dry fruit largely decreases the number of 

 spots which subsequently develop. 



Splitting. 



In Barbados the shaddock is especially liable to this trouble- 

 It is caused by failure of the rind to keep pace in growth with 

 the contents of the fruit. This may be caused by surface injuries 

 due to scale insects or fungi, and apart from these sometimes 

 appears to be brought about by irregularities in conditions. 

 Increased shelter, tillage, mulching, and avoidance of sudden 

 heavy waterings are measures calculated to prevent the occurrence 

 of splitting. 



Blue Mould, 



The soft rot of stored fruit due to blue and green moulds of 

 the genus Penicillium is universal and familiar. All experience 

 shows that these fungi are rarely or never able to obtain a footing 

 on sound uninjured fruit, but that any scratch, or a slight and 

 imperceptible bruise may suffice to afford an entry and cause 

 the rotting of the whole fruit. It is this fact which calls for 

 the most meticulous care in handling fruit which is to be stored 

 or shipped — a necessity which it would appear impossible for 

 the heavy-handed West Indian labourer ever to be made to 

 appreciate. Reference on this subject should be made to 

 Chapter XIII. 



The course of this type of rot comprises, first, a progressive 

 softening around the point of infection ; second, the appearance of 

 white mycelium extending over the surface of the softened spot ; 

 and third, the production from this mycelium of conidia in dense 

 masses, forming a blue or green layer, and discharged as dust 

 clouds when disturbed. 



Charcoal Rot. 



An affection described by 0. T. Wilson as occurring on 

 Florida limes has been several times met with on West Indian 

 oranges bought in Barbados. In the fresh fruit it is recognisable 

 by the presence of surface areas, smooth in comparison with the 

 normal surface and more or less discoloured, the colour varying 

 from a deepened yellow to copper colour, with the margin of the 

 spot mostly brownish. Upon opening a diseased fruit an abnor- 



