On Evil in Small Doses 



A great many other cases might be quoted to show 

 how general seems to be this law, viz., that something 

 evil is an excellent stimulus if administered in small 

 doses. But it will be better to show exactly what 

 happens in crises of this kind. 



Certain gladiolus bulbs were carefully tested in order 

 to find out the exact amount of carbonic acid given off 

 in ordinary respiration. These bulbs were then treated 

 with the utmost cruelty. Some were poisoned with ether, 

 and were found to breathe five times as quickly as they did 

 under normal conditions ; others were placed in a high 

 temperature, and these also breathed at double the rate. 



Some were submerged in cold water for twenty-four 

 hours, and others were bruised and injured in various 

 ways, but in every case the result was a more rapid and 

 intense respiration. 14 



When onion bulbs are cut or slashed, every wound 

 increases the amount of carbonic acid given off in 

 respiration. 



When potatoes are cut, or the seedlings of various 

 vegetables are injured by removing the root-tip or slicing 

 the cotyledons, the respiration increases in every case, 

 and only becomes normal after the wound has been 

 healed. 15 



But it has also been found that when plants are 

 suffering from the attacks of fungi or of insect enemies, 

 their respiration is more intense. Not only so, but when 

 a rust-fungus has established itself upon a living plant, 

 all the normal life-processes are intensified and accele- 

 rated. More water is given off in transpiration, more 

 sugar and other material is produced by assimilation, 

 and the breathing is also more rapid and vigorous. 16 



We have already mentioned the efforts made by a 

 leaf to cut out an injured spot by a sort of surgical 

 operation performed of its own initiative. The growth 



33i 



