48 DISEASES OF CULTIVATED PLANTS 



The section of a fasciated tip shows no deviation from the 

 normal structure other than that of shape. Below the 

 fasciated region inequalities in the amount of wood formed 

 are indicative of the early injury. 



The progeny of fasciated plants shows no more tendency to 

 fasciation than that of normal stock. Both may give an 

 equally large percentage of fasciated stems. 



Knox, Fifth Year Book of the Carnegie Inst. of Washington , 

 p. 131 (1907). 



Worsdell, W. C., ' Fasciation : Its Meaning and Origin,' 

 New Phytologist, 4, p. 55 (1905). 



BACTERIOLOGY OF THE SOIL 



'Soil fertility, broadly interpreted, denotes the crop- 

 producing power of any soil under given climatic conditions, 

 and is itself the resultant of many forces often opposed to 

 one another.' The above definition of fertility given by 

 Voorhees and Lipman is terse and to the point, and the rider 

 suggests with equal terseness the difficulties to be overcome 

 in formulating in a concise manner the causes that culminate 

 in such fertility. 



The earliest scientific attempts to investigate the means 

 whereby soil furnishes food for plants were undertaken by 

 chemists, who, however, soon discovered that chemical 

 methods alone would not solve the problem. Then followed 

 researches from a physical standpoint, and much valuable in- 

 formation on soil-fertility is the outcome of soil physics. 



At a still later period the part played by micro-organisms or 

 bacteria in connection with the fertility of the soil was recog- 

 nised, and it is now universally acknowledged that further 

 progress bearing on the subject of plant nutrition will mainly 

 result from the combined work of the chemist, physicist, and 

 bacteriologist, and every scientific student of agriculture 

 realises the supreme influence exercised by bacteria present 

 in the soil on plant life. 



It has long been known that poor, uncultivated land in 

 process of time becomes capable of producing a good crop ; 

 in other words, such land increases in fertility. The following 

 quotation from Hall bears on this point : 4 How comes it that 

 Geescroft land, with no plants growing on it which are capable 



