PESTS. 53 



The vegetative form of a fungus consists of mycelium or 

 hyphae, which performs similar functions in the way of obtaining 

 and assimilating nutriment for the fungus plant as roots and 

 leaves perform for flowering plants. With few exceptions, the 

 mycelium of parasitic fungi remains within the tissues of the 

 host plant, so that the casual observer only sees the fruiting or 

 reproductive stage, by which time the fungus has completed its 

 work of destruction. It will thus be seen that, notwithstanding 

 the fact that the reproductive form of the fungus has been found 

 on dead tissues, it does not follow that it is a saprophyte, as it 

 may have killed them ; nor does it follow that because a fungus 

 has been discovered growing on dead tissues that it has killed 

 them. 



The commonest method of infection is by spores, which 

 for all practical reproductive purposes may be considered to take 

 the place which seeds occupy in regard to flowering plants. 

 Spores are minute bodies of various colours and shapes, many 

 thousands being required to cover a threepenny bit. These are 

 produced in enormous quantities, and are readily distributed by 

 wind, rain, insects, animals, man, and numerous other agencies. 

 Any which alight on a suitable host germinate and spread the 

 disease. 



The difficulties attending the attempts to exterminate fungus 

 diseases have been frequently demonstrated, and as examples 

 may be quoted those employed in regard to " rust in wheat," 

 vine mildew, and coffee-leaf disease. Too great stress cannot 

 be laid on the necessity for adopting preventive methods by 

 promoting sanitary conditions on the plantation, proper cultiva- 

 tion, selecting seeds from healthy plants, and burning diseased 

 tissues. 



Always have a stock of fungicides and apparatus, such as 

 sprays, to apply them, at hand to treat a disease in its early 

 stages, for it is then often possible to check and even exterminate 

 it, whereas this may be impossible later. The most favourable 

 conditions for the development of parasitic fungi are " heat " and 

 " moisture." Sunlight is an important factor in checking them, 

 so that closely planted estates offer more favourable conditions 

 for the spread of disease than where trees are planted wider 

 apart. 



