A. M. Taylor 257 



termination of this period, microscopic examination shewed that infec- 

 tion of those cuttings kept under moist conditions had taken place 

 in much the same proportion as those previously kept under the same 

 conditions, and that those kept under dry conditions remained un- 

 affected. The roots made freely by the cuttings under both dry and 

 moist conditions and also the stems were found upon dissection to 

 be free from worm. 



From the united evidence of these experiments it may be said that 

 migration from the soil to the buds occurs only when the medium of 

 moisture is present which enables the worms to reach their destination. 

 It also confirms the ectoparasitic habits of the worms, for it is reasonable 

 to suppose, seeing that the worms and the roots started into activity 

 at much the same time, that the latter, had the worms penetrated 

 them when they were in a rudimentary condition, would at least have 

 had their growth checked or entirely suspended. This experiment 

 also opens up the question of the suspension of the life of the worm 

 under conditions of drought, which phenomenon will be discussed later. 



Having thus ascertained that migration and distribution of the 

 worm occur under conditions of moisture, it became necessary to 

 consider the effect on migrating worms of these conditions as they 

 occur in the open. 



The following sections are therefore an endeavour to produce such 

 conditions artificially in the laboratory, an attempt which, although 

 clumsy as such experiments must be, yet gave results which are 

 probably somewhere near the truth. They deal with conditions of 

 an extreme nature, i.e., the influence of heavy rain and of light rain 

 or mist. 



Section III. 



An endeavour was made to ascertain : — (i) whether worms under 

 the influence of heavy rain could ascend from the soil to the apical buds 

 of the seedlings if infection were restricted to the soil, and (ii) whether, 

 if infection were in like manner restricted to the apical buds, they 

 could infect those buds situated on the stem below them. 



The seedlings required for this experiment were therefore divided 

 into two series, in one of which infection was brought about as in the 

 previous experiments by soil inoculation and in the other by bud 

 inoculation, in which case colonies of worms were inserted directly 

 into the bud scales of the terminal and apical buds. Both series were 

 kept under identical conditions and the effect of heavy drops of rain 



