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finest dust. After a brief rest the zoospores burst, and 

 produce a thread of spawn. This thread is capable of 

 carrying on the existence of the potato fungus. These 

 tiny zoospores are easily transported on the air, or 

 by birds, insects, or other agency, and if they alight 

 on a potato plant, thrust their thread of spawn 

 into the leaf, and establish themselves in the plant. 

 As bearing on the prevention of the disease by means 

 of spraying with the Bouillie Bordelaise, or sulphate 

 of copper and lime solution, the marvellous instinct 

 these zoospores possess of recognising when they have 

 found a suitable host on which to establish themselves, 

 is worthy of notice. If the germinating zoospore produces 

 its thread of spawn on any substance but part of a potato, 

 tomato, or other solanaceous plant, the thread does not 

 attempt to pierce it, and the zoospore shortly dies. 

 But if it falls on a potato plant more readily if on the 

 leaf the thread of spawn at once endeavours to force 

 its way into the plant; and this is rendered more 

 easy because the tip of the thread is furnished with a 

 substance which is of the nature of ferment, possessing 

 the power of dissolving its way through the outside of 

 the leaf. It is by rendering the surface of the leaf 

 obnoxious to the little thread cf spawn, by covering 

 the leaf with a thin film of copper, that the disease 

 does not enter plants which have been sprayed 

 with the Bouillie Bordelaise. The stem is liable to 

 attack, as the zoospore can pierce through the skin 

 and find its way to the cells. Deep moulding-up of 

 potatoes prevents, to some extent, the disease attack- 



