296 



Blackleg in Potatoes. 



[AUG., 



belonging- to the lenticels behind, hence the surface of the tuber 

 is covered with little groups of dead cells. 



The mycelium of fungi that happens to be in the soil sur- 

 rounding a tuber thus formed, finds suitable food in the dying 

 or dead superficial cells. When the fungus penetrates suffi- 

 ciently to reach the deeper living cells, the irritation set up by its 

 presence causes the living cells of the tuber to divide quickly 

 and form a wall of cells specially constructed to check the 

 progress of the fungus into the interior of the potato. By this 

 means the warts are built up by the tuber in its endeavour to 

 arrest deeper penetration by the fungus. 



Young tubers were carefully exposed without disturbing their 

 continuity with the parent plant, and infected with cultures of 

 the fungi mentioned above, and in course of time the warts 

 formed on these tubers contained the same kind of fungus as 

 that used for infection. 



The check potatoes grown in sterilised soil remained free 

 from warts. 



The above experiments prove that the primary cause of the 

 disease of " Evergood " potatoes is due to the excessive develop- 

 ment of the lenticels in this particular variety. The dead cells 

 situated over each lenticel favour the attacks of various kinds of 

 fungi present in all soils, which could not gain an entrance into 

 the tuber through the unbroken surface of the skin or periderm. 



A further scientific account of these experiments will be 

 given elsewhere at a later date. 



The attention of the Board was recently called to a disease 

 occurring among potatoes in Cheshire, and reported to be very 

 destructive. A specimen, accompanied by 



B potatQ^s in the haulm > was forwarded to the Royal 

 Botanic Gardens, Kew, and proved to be 

 a typical example of the "blackleg," or potato stem rot, des- 

 cribed in Leaflet No. 117. 



The leading symptoms of the disease are as follows*: — The 

 leaves wilt and turn yellow ; then they become shrivelled ^from 

 below upwards, and finally die. If the underground portion of 



