INORGANIC CONSTITUENTS OF PLANTS. Ill 



Inorganic Constituents, and their Sources. 



219. The consideration of the inorganic constituents of plants is no 

 less important than the study of their organic elements. The organic 

 substances formed by plants are decomposed by a moderately high 

 temperature ; they easily undergo putrefaction, especially when ex- 

 posed to a moist and warm atmosphere, and they have not been formed 

 by human art. Their inorganic constituents, on the other hand, are 

 not so easily decomposed ; they do not undergo putrefaction, and they 

 have been formed artificially by the chemist. 



220. The combustible or organic part of plants, even in a dried 

 state, forms from 88 to 99 per cent, of their whole weight. Conse- 

 quently, the ash or inorganic matter frequently constitutes a very small 

 proportion of the vegetable tissue. It is not, however, on this account 

 to be neglected, for it is found to be of great importance in the 

 economy of vegetation, not merely on account of its entering directly 

 into the constitution of various organs, but also from assisting in the 

 production of certain organic compounds. Some of the lower tribes of 

 cellular plants can exist apparently without any inorganic matter. 

 Thus Mulder could not detect a particle of ash in Mycoderma vini, 

 nor in moulds produced in large qiiantity by milk siigar. Deficiency of 

 inorganic matters, however, in general injures the vigour of plants, and 

 it will be found that, in an agricultural point of view, they require 

 particular attention a distinct relation siibsisting between the kind and 

 quality of the crop, and the nature and chemical composition of the 

 soil in which it grows. It has been shown by careful and repeated 

 experiments, that, when a plant is healthy and fairly ripens its seeds, 

 the quantity and quality of the ash is nearly the same in whatever 

 soil it is grown ; and that, when two different species are grown in the 

 same soil, the quantity and quality of the ash varies the difference 

 being greater the more remote the natural affinities of the plants are. 



221. The inorganic elements of plants and their combinations, are 

 thus given by Johnston: 



Chlorine (Cl.) combined with metals forming chlorides. 

 Iodine (I.) ... ... metals ... iodides. 



Bromine (Br.) ...... metals ... bromides. 



f ...... metals ... sulphurets. 



[_ ...... oxygen ... sulphuric acid. 



Phosphorus (P.) ... ... oxygen ... phosphoric acid. 



p . , , f ...... oxygen ... potassa. 



*> \ ...... chlorine ... chloride of potassium. 



( ...... oxygen ... soda. 



Sodium (Na.) < ,, (chloride of sodium. 



j ... ... chlorine -< / , , 



( ( (common salt. ) 



p ol , fr < -, \... ... oxygen ... lime. 



Calcium (L/a.) ,,- . ,, . -, e , . 



(... ... chlorine ... chloride of calcium. 



