THE CULTURE OF THE POTATO. 55 



Bordeaux Mixture is made by using 1 Ib. copper 

 sulphate and Ib. freshly burnt- quick-lime in 10 

 gallons of water. Prepare as above, but it is neces- 

 sary to strain the lime fluid through a piece of fine 

 material to remove all gritty matter. 



Larger quantities may be made on the same lines, 

 but using the materials in the above relative pro- 

 portions. Either of these mixtures should be used 

 soon after being made, for they deteriorate by stand- 

 ing any length of time, and may become injurious to 

 the foliage. 



Wart Disease (Synchytrium endobioticum). This 

 is the most serious and destructive of all the diseases 

 affecting potatoes, and when it finds its way into a 

 locality, or a single garden, it becomes a menace to 

 a large area. The disease gains an entrance at the 

 eyes of young undeveloped potatoes, and there 

 causes the growth of warty excrescences. One eye 

 or several may be affected, but in late summer and 

 autumn the diseased tubers become more or less 

 covered with a rough warty mass and are rendered 

 useless. (See Fig. 7.) The stems ot the plants above 

 the soil level may show the disease in the form of 

 greenish- white outgrowths, and this is often the first 

 indication of the presence of the fungus. (See Fig. 8.) 

 At first the warts on the tubers are brown in colour 

 and quite firm, but later they become almost black, 

 and in autumn they turn quite soft and rot away. 

 It is mainly when the last-mentioned stage is reached 

 that immense numbers of spores of the disease escape 

 into the soil, where they remain dormant but retain 

 their power of infecting a potato crop for several 

 years, and during all that time there is the constant 



