i86 THE BOOK OF NATURE STUDY 



burst, scattering the spores, which, if conditions of warmth, 

 moisture, and presence of the host plant are favourable, germinate 

 and give rise to fresh infection. Continuity of the life of the 

 fungus is maintained by means of resting spores, which remain 

 dormant during the winter and resume growth in the following 

 summer. 



To prevent the disease, care should be taken to burn all diseased 

 leaves and stalks. Diseased tubers may be fed to pigs after being 

 first thoroughly cooked by boiling. 



Fortunately, the disease may be successfully combated in its 

 early stages by spraying the plants with Bordeaux mixture, and 

 as the disease is so common it is advisable to spray all Potato 

 crops whether the presence of the fungus has been observed or 

 not. Bordeaux mixture is made as follows. Dissolve 10 ounces 

 of crystalline copper sulphate in half a gallon of water. Take 

 half a pound of quicklime and slake it by adding water to it a 

 little at a time until the lime becomes hot and crumbles to a 

 powder. When cool add to it 12 to 15 gallons of water in a tub 

 and stir once or twice. Allow to settle, and, when clear, measure 

 out 8J gallons of the lime water and mix it with the copper sul- 

 phate solution. Add sufficient water to make up to 10 gallons. 

 Copper sulphate solution cannot be made in a metal vessel owing 

 to the chemical action which would take place. A wooden tub 

 should be employed. For spraying use a knapsack sprayer, and 

 in applying the jet of liquid endeavour to get as much as possible 

 on the under surfaces of the leaves. For this purpose one operator 

 should direct the spray while a second turns up the leaves with a 

 stick. The first spraying should be carried out at the beginning 

 of July, and should be repeated once or twice at fortnightly 

 intervals. 



BIBLIOGRAPHY 



GENERAL GARDENING. (a) Thompson's Gardeners' Assistant, published in 

 six volumes at 8s. each, or in two volumes at 253. each, (b) Sanders, Encyclopedia 

 of Gardening. 35. 6d. (c) Board of Agriculture : Sectional volumes of Leaflets, 

 namely" No. 5. Fruit Trees and Farm and Garden Crops." Percival, Artificial 

 Manures and how to use them in the Garden, Orchard, and Allotment. 6d. 



SPECIAL SECTIONS OF GARDENING. (a) Wythes, The Book of Vegetables. 2s. 6d. 

 (b) Thomas, The Book of the Apple. 2s. 6d. (c) Arnott, The Book of Bulbs. 2s. 6d. 

 (d) Report of the Departmental Committee on Fruit Industry. Cd. 2589. 4jd. 



