Value of Potash 



how this scalding arises is not very clear, but it 

 is probably due sometimes to a great local rise of 

 temperature leading to the too rapid withdrawal of 

 water from the cells, and at others to a rapid fall 

 in temperature perhaps bringing about a similar 

 result, and in any case leading to the death of cells 

 in circumscribed areas in the leaf. The preventive 

 must be found by a consideration of all the circum- 

 stances and the removal of the cause, adjusting 

 matters so as to maintain a proper degree of moisture 

 in the air in relation to the temperature of the house 

 and the amount of light the plants are receiving. 

 This is, of course, difficult to achieve for every plant 

 when many kiads of plants are grown in one house, 

 and it then becomes a question whether attempts 

 should be made to cultivate any others than the 

 more accommodating ones, or in the alternative to 

 restrict the inmates of the houses to some special 

 favourites with similar requirements. 



Returning now to the effect of the chemical 

 constitution of the soil on health, we find that an 

 excess of any or a deficiency of the ordinary earth- 

 salts produces more or less definite symptoms. 

 We have already pointed out the more obvious parts 

 played in plant nutrition by the principal chemical 

 eleinents, and the result of a deficiency of any one of 

 them is readUy seen. It only remains to say that 

 deficiency in potash supply lays many plants open 

 more readily to fungus attack, and that deficiency 



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