1910.] PUBLIC DOCUMENT — No. 31. 155 



system also have been observed where an excessive amonnt of 

 nmriate or carbonate of potash had been applied, and an excess 

 of tannin, such as is found in the sawdnst from certain trees, 

 will canse the roots of plants to turn yellow and eventually die. 



The effects of chemical substances on roots are not always 

 the same, although ultimate death may follow their use. Certain 

 chemical substances, on coming into contact with the roots, may 

 merely cause plasmolysis of the cells. The immediate result 

 here may not be death of the cells, but if the cells remain in a 

 state of plasmolysis for any length of time, the collapse of the 

 plant follows. 



Any substance in the soil which aifects the osmotic tension or 

 turgidity of the cell would naturally })revent root absorption, 

 and if the plant was trans])iring very freely it would sooner or 

 later w^ilt and collapse. On the other hand, a large number of 

 chemical substances act as direct poisons to the protoj^lasm, kill- 

 ing it the moment of contact. 



By far the largest nuud)cr of cases of malnutrition which have 

 been brought to our notice arc found in greenhouse plants, al- 

 though outdoor crops are by no means wholly free from it. ( on- 

 ditions in a greenhouse are entirely different from those out- 

 of-doors. The frequent rainfalls, together with the action of 

 frosts in winter, naturally hasten the process of leaching, and 

 soil in the field which might become abnormal from injudicious 

 fertilizing is kept in a normal condition. In the greenhouse 

 the leaching is not so thorough, since the water and plant food 

 are usually confined to the surface in a concentrated form. 

 Moreover, in the greenhouse new supplies of plant food are being 

 constantly added, and in the end do harm. When the soil is 

 treated with hot water or steam, as is often the case, additional 

 soluble food becomes available, which, in a soil already rich, is 

 likely to produce ideal conditions for malnutrition. It would 

 appear from the results of our experiments and observations that 

 by far the greater amount of troul)le from malnutrition comes 

 from excess of nitrates in the soil. 



Some years ago a potted specimen of a Johnsonian lily which 

 had a number of eruptions or blisters on its leaves was called 

 to our attention. These reddish blisters, on careful examination, 

 showed no evidence of the presence of fungi or insects. The 



