42 



they are merely organs of attachment. Large disks (hypho- 

 podia) are also frequently developed which evidently serve as 

 organs for attaching the mould to the leaf. Reproductive 

 bodies of several forms are developed in great abundance, and 

 these are easily carried from tree to tree or from grove to grove 

 through the agency of the wind, insects, birds, or animals. 



This disease injures the plant by interrupting the process of 

 assimilation This is brought about by the cutting off of light 

 and by hindering the passage of necessary gases in and out of 

 the plant. The accompanying insects further injure the plant 

 by sucking the nutritious juices from the cells of the leaves. 

 The growth of the tree is usually greatly retarded, and in 

 serious cases is frequently entirely checked until some relief 

 is found. The blooming and fruiting are commonly light, and 

 in very bad cases are wholly suppressed. In slight droughts 

 the leaves wither quickly and curl up, resembling those on 

 blighted trees. The young fruit becomes covered with the 

 sooty mould and is retarded in its development, frequently 

 never reaching complete maturity. It is usually smaller and 

 less juicy than that normally developed, and remains very 

 insipid. It does not change to the normal bright orange 

 colour of mature fruit until very late, and if the membrane of 

 the sooty mould covering it is quite thick the rind remains 

 somewhat green, apparently for an indefinite period, rendering 

 the fruit unsaleable. The black coating formed by the sooty 

 mould renders the fruit unsightly and unsaleable until it is 

 thoroughly washed, which necessitates a considerable expendi- 

 ture of time and labour. Even when carefully washed, a 

 process which injures the keeping quality of the fruit, much of 

 it being still small and green is unlit for market. 



Treatment. — Where sooty mould followed the attacks of the 

 orange mealy wing, spraying with resin wash or fumigation 

 with hydrocyanic acid gas was found to be very effective. 

 "When resin wash (4) is used, the best time for treatment is in 



(4) The following is the formula for resin wash: Kesin, 20 lbs.; 

 caustic soda (98 per cent.) 4£ lbs.; fish oil (crude) 3 pints; water to 

 make 15 gallons. Place the resin, caustic soda, and fish oil in a large 

 kettle. Pour over them 13 gallons of water and boil till the resin is 

 thoroughly dissolved, which requires from three to ten minutes after 

 the materials begin to boil. While hot add enough water to make just 

 15 gallons. This may be most readily accomplished by taking a tight 

 keg or other tall receptacle and measuring into it 15 gallons of water. 

 Then plainly and permanently mark the height to which the 15 gallons 

 reach, ^fter boiling the hot solution may be poured directly into this 

 measuring keg and sufficient water added to bring it up to the 15 gallon 

 mark. This serves as a stock preparation. 



When this stock preparation cools, a fine yellowish precipitate forms 

 and settles to the bottom of the vessel. T he preparation must, there- 



