254 Black Currant Eelworr^i 



In dealing with migration, the necessity was evident for discovering 

 the degree of susceptibiUty of the worm to the atmospheric conditions 

 which maintain in the open. 



An experiment having this object in view was carried out in the 

 laboratory roof greenhouse, the isolated position of which rendered 

 infection from any source remote. Black currant seedlings raised for 

 the purpose under sterile conditions were used as host plants and the 

 experiment was carried out during the winter months, while the buds 

 were in a resting condition. The greenhouse was maintained at an 

 equable temperature, and the water used for spraying and for ordinary 

 watering, was distilled. Both soil and pots used throughout the experi- 

 ment were sterilized. Inoculation was effected either by placing buds 

 detached from infected material on the soil round the seedlings, or 

 by directly introducing colonies of worms between the scale leaves of 

 the buds. The experiment was continued over a period of six weeks 

 from the date of inoculation, after which the buds which averaged 

 150 in number exclusive of controls in each section, were micro- 

 scopically examined. 



On material thus prepared, it was hoped, by the strongly contrast- 

 ing conditions of drought and moisture, to gain information on the 

 following points : — 



(i) Whether migration could take place under conditions in which 

 moisture is entirely withheld from the vegetative parts. 



(ii) Whether at the other extreme it can be successfully carried 

 out if the vegetative parts are subjected to an excess of moisture. 



(iii) Whether an occasional vigorous application of moisture to 

 resemble heavy rain influences migration. 



(iv) And whether a similar light application resembling light rain 

 and mists yields identical results. 



Section I. 



Whether migration can take place under conditions in which 

 moisture is entirely withheld from the vegetative parts. 



The aerial portions of the seedlings used for this experiment were 

 kept under conditions of drought, the buds and stems receiving no 

 moisture in any form. Watering of the soil was however performed 

 when necessary to keep the plants alive, and to ensure the activity of 

 the worms with which the plants were inoculated. 



It became necessary before this experiment was started to remove 

 the basal buds immediately above the soil surface, for these became 



