152 PLANTING IN UGANDA 



leaf. In course of time, the leaf ceases to provide 

 food for the fungus, and the latter then bursts 

 through the skin of the leaf and bears on its sur- 

 face a crop of spores, which are scattered by wind, 

 birds, insects, etc., and infect other leaves. In 

 reality the leaf was diseased from the moment the 

 sprout of the spore entered its tissues, although 

 sometimes weeks passed before there was any out- 

 ward sign of the presence of the parasite in those 

 tissues. 



This statement is true of hundreds of kinds of 

 fungi that are parasitic on plants both wild and 

 cultivated ; in fact, it is true of all parasitic fungi, 

 with the exception of a few mildews, of which the 

 Hop mildew and Eose mildew are examples. Such 

 being the case, it is quite obvious that the only way 

 to guard against infection from the spores of fungi 

 is to prevent their entrance into the leaf, and 

 spraying with a fungicide is the only known 

 method of accomplishing this object. We are 

 quite well aware of the many practical difficulties 

 standing in the way of spraying in the tropics- 

 torrential rains, nature of the ground, labour, etc., 

 yet in very many instances spraying could be 

 practised with decidedly beneficial results. 



