108 



Scientific Proceedings, Royal Dublin Society. 



Inasmuch as growth was not sensibly retarded for some three weeks following 

 the operation, and then not very marliedly, it is to be presumed that both water 

 and solutes continued to ascend the stem, and that consequently no pronounced 

 blocking of the tracheae occurred as a result of morbid clianges spreading inwards 

 through the wood-parenchyma and rays from the injui'ed region. The antiseptic 

 properties of the poisonous latex are doubtless in some measure responsible for 

 this. 



Inspection of the graphs in the figure will make it clear that the fluctuations 

 in temperature and rainfall provide no adequate basis for interpreting the changes 

 observed in the rate of growth. 



II 16 21 



T/'me in Weeks 



?6 



Records were also kept of wind-velocity and evaporation, but are not presented, 

 as no significant relationship can be traced between these factors and the changes 

 in the rate of growth. The period the sun was above the horizon varied by just 

 one hour and a quarter during the period occupied by the experiment. 



The subterranean environment was kept as uniform as possible ; a dust mulch 

 was maintained, and water added whenever it was suspected that growth might 

 be limited by a reduction in the water-supplying power of the soil. 



