94 VEGETABLE PARASITES AND EPIPHYTES 



some writers of describing these various diseases under 

 sub-heads in accordance with the particular portion of 

 the tree which they generally affect, as some of the pests 

 attack indiscriminately several portions of the tree above 

 ground. 



Losses sustained through Fungus Diseases. — The tre- 

 mendous losses which agriculturists in different parts of 

 the world have suffered from the ravages of parasitic 

 fungi should be sufficient to convince the cocoa planter 

 of the advisability of adopting suitable prophylactic 

 measures with a view to protecting his trees from similar 

 epidemics. 



Rust in Australian wheat, during the season 1890-1, 

 is estimated to have robbed the farmer of £2,500,000 

 sterling. During the latter year the ravages of parasitic 

 fungi in Prussian cereal crops are estimated to have 

 entailed a loss amounting to £20,500,000 sterling. The 

 Ceylon coffee-leaf disease is reported to have resulted 

 in a loss of nearly £15,000,000 sterling in ten years. 



The cocoa planter should make himself acquainted 

 with the general habit and the name of the commonest 

 groups of the fungus parasites of plants, their means 

 of attack, and the conditions which best favour their 

 development. He should also bear in mind that many 

 of the fungi are facultative. The saprophytes, which 

 generally live on dead organic matter, may assume a 

 parasitic habit, and parasitic fungi may in turn adopt 

 saprophytic habits. Mycelium, or hypha, which con- 

 stitutes the vegetative form of a fungus, performs similar 

 functions in the way of assimilating nourishment for the 

 fungus plant as roots and leaves perform for flowering 

 plants. 



The mycelium of parasitic fungi, with comparatively 

 few exceptions, remains within the tissues of its host. 

 The casual observer therefore only sees the fruiting 

 or reproductive stage when that particular fungus plant 

 may have completed its destructive work. Consequently 

 it does not follow that because the reproductive form 

 of a fungus has been discovered on dead tissues, it is a 

 saprophyte, as it may have been the cause of their death. 

 In the same way a particular fungus must not be con- 

 sidered responsible for the death of plant tissues because 

 it is found growing on them, as it may be a saprophyte. 



