20 DISSEMINATION OF PARASITIC FUNGI 



The fungi which cause rotting of ripe fruit are readily conveyed on 

 consignnxents of fruit. A recent case reported^ was on 

 oranges from Brazil, the sea passage being about 18 days. 

 Other cases known are on pineapples and bananas from the 

 West Indies and citrus fruits from South Africa. 



The diseases of such crops as cacao and rubber, the cultivation of 

 which has been started in many tropical countries in com- 

 paratively recent times, should furnish interesting instances 

 of the spread of fungal parasites through the agency of man. 

 Rubber is often sent considerable distances as young cut-back 

 plants, known as " stumps," and the first Para-rubber sent 

 to Ceylon and Singapore from Kew in 1875 was in the form 

 of seedlings. In cacao also the large fleshy pods would be an 

 excellent medium for conveying living fungi. Unfortunately 

 we are as yet by no means fully acquainted with the parasites 

 of these crops in difierent countries and several of their 

 worst diseases are caused by species which attack a number 

 of other jjlants and which there is no reason to think are 

 introduced. The canker fungus, however, is only known on 

 these two crops (and possibly the bread fruit), and as it is 

 now found in most countries of both the eastern and western 

 hemispheres where they are grown, it seems to be highly 

 probable that it has travelled with the host plant. 



There are several diseases that from their very nature are unlikely to 

 be carried in any other way than on their victims, in soil, or 

 in packing. The warty disease of potatoes is a case in point ; 

 if we could keep potatoes from infected localities out of those 

 still free, it is scarcely possible that the fungus could spread 

 more than a very limited distance indeed. This is because the 

 spores are confined to the tubers and are only set free into the 

 soil when the latter decompose. The finger-and-toe disease of 

 turnips, cabbages, etc., is a similar case ; it is still unknown 

 in India, though reported in Ceylon as an introduced disease. 

 Other instances are the diseases of lucerne caused by Urophlyctis 

 AlfalfcB and the grass disease caused by Cladochyfrium graminis. 

 The latter disease was recorded in Great Britain for the first 

 time in 1908 and appeared in every instance where portions 



' Bushton, W., in Ann. Applied Biology, I,[_1915, p. 365, 



