242 TEANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



tion of potassium permanganate. This is a salt which 

 readily parts with a portion of its combined oxygen and 

 it might be supposed, would be able to supply the radicle 

 with the oxygen necessary to permit of its growth and 

 downward curvature. It is found however that the salt 

 itself exercises a repellant irritant action upon the radicles, 

 whilst if these remain immersed in the solution for some 

 time they become covered with a brown deposit, and are 

 finally killed by the action of the permanganate solution. 



The same experiments performed with Hemp and Wheat 

 seedlings gave similar results. Owing to the fact that in 

 the case of Hemp the entire seedling including the 

 cotyledons escapes from the enclosing husk it is necessary 

 to fix the seedling shortly after germination has taken 

 place. Hemp seedlings do not seem to be so sensitive to 

 the absence or deficiency of oxygen as are Peas, their 

 oxytropic irritability being less marked. The radicles 

 even when deeply immersed go on growing, though the 

 rate of growth is much slower than usual. 



In the case of the Wheat seedlings we are of course 

 dealing with secondary roots but these also shew a similar 

 irritability, for on coming into contact with water devoid 

 of oxygen, they either grow along the surface or grow 

 upwards and away from it. As soon as they reach a 

 certain length owing to their thin and slender nature their 

 own weight causes them to bend downwards but that 

 is quite a different thing from the apically produced 

 curvature caused by exciting either the geotropic or the 

 oxytropic irritabilities. 



As in the case of Hemp and Peas if the tips of the 

 radicles are immersed two or three inches beneath the 

 surface upward curvatures cease to appear. 



