x DISEASES OF CULTIVATED PLANTS 



FACTS NOT GENERALLY KNOWN 



PAGE 



Spraying alone not sufficient Crowding of plants of one kind 

 favours spread of disease How land becomes infected 

 Diseased material and spread of disease Danger attending 

 use of humus and leaf-soil, . ...... 23-26 



WOUNDS 



Self-pruning Dangers attending injudicious pruning Injuries 



caused by man Injuries caused by wind, snow, etc.. . . 27-30 



DROUGHT 



Stag-headed trees, causes and prevention, .... 30 



INJURIES DUE TO FROST AND HAIL 



Spring frosts Frost cracks Glassy fir Injury caused by hail. 



Wound-fungi often follow wounds made by frost and hail, . 30-34 



CHLOROSIS 



Effect of chlorosis on plants Causes of chlorosis Remedies 



Contagious chlorosis Grafting experiments, . . . 34-38 



INJURY BY SMOKE, ACID FUMES, GAS, ETC. 



Sulphur dioxide specific cause of injury from smoke Physio- 

 logical effects Coal gas Creosote fumes, .... 38-40 



INTUMESCENCES OR WARTS 



Causes Sap-warting Warts caused by spray solutions, . . 41-45 



FASCIATION 



Postgenital and congenital forms of fasciation. Sometimes due 



to injury to growing-point, ....... 45-48 



BACTERIOLOGY OF THE SOIL 



P'ixation and liberation of nitrogen in the soil by bacteria 

 Fertility of soil increased by treatment with carbon bi- 

 sulphide, 48-51 



ECONOMIC ASPECT OF PLANT DISEASES 



Constant losses from small and unobserved diseases causes more 



loss than that due to epidemics Statistics of disease, . . 5I-5 2 



