CHAPTER X 

 NUTRITIVE AND STIMULATIVE FUNCTIONS OF SALTS 



Out of the dead, cold ashes life again. 



—J. B. Tabb. 



The Ash. — It has been pointed out in Chapter III that a plant 

 can be divided into three portions, viz., a watery portion varying 

 from 40 to 95%, a combustible portion ranging from 1 to 55%, 

 and an incombustible residue of ash of from 1 to 5%. The water 

 may be driven out by heating in an oven at a temperature of 

 105° C. ; when the plant no longer loses weight at this temperature, 

 it can be assumed that all the water has been driven off. To elim- 

 inate the combustible material which makes up the bulk of the 

 dry matter, the plant must be incinerated, under which condition 

 the carbohydrates, fats, proteins, etc., are oxidized and pass off 

 into the atmosphere as gases. The carbon, oxygen, hydrogen, 

 and nitrogen of the plant are thus driven off; and if the residue is 

 then analyzed, it will be found to consist chiefly of oxides of the 

 various minerals called the ash. 



These ash elements function in the plant for the most part 

 in one of three ways. (1) They may enter into the composition 

 of the plant substance, in which case they are said to be nutritive. 



(2) They may cause by their presence certain processes and re- 

 actions to take place, which would not occur in their absence. 

 In this respect they act either like enzymes (Chap. XVI) or vita- 

 mins (Chap. XVII), and for this general type of function, we may 

 use the term stimulative. Since it is frequently difficult to separate 

 these two functions, they are treated together in this chapter. 



(3) The substances may counteract the effects produced by some 

 other element present. This balancing function, due, in general, 

 to the fact that electrical charges come into play when matter 

 in an ionic state is concerned, will be considered in the next 

 chapter. 



A total of over thirty elements have been found in plant ash 

 including the following: 



100 



