2 4 o PLANT AND ORGANIC CHEMISTRY 



of their fixed ingredients." 1 If an ash-constituent can pass 

 through a cell wall, its absorption will take place independently 

 of its use or harmfulness to the plant, but the absorption of es- 

 sential inorganic constituents will depend upon its relation to 

 the metabolism of the plant. 



The ash- constituents of a plant increase from the roots up- 

 wards to the leaves, a fact showing that the leaves are the organs 

 in which more especially active chemical changes take place. 



The ash ingredients are usually present in each plant cell; in 

 the cell wall, imbedded in the cellulose, and partly in the con- 

 tents of the cell. The salts of the alkaline metals and of the sul- 

 phates and the chlorides of magnesium and calcium occur in 

 the solution of the sap. Silica and phosphates of calcium and 

 magnesium are mostly insoluble and exist in the tissues of the 

 plant. 



Water- culture experiments 2 have shown the essential ash- 

 ingredients. Potassium, like phosphorus, is always found in 

 relation with living protoplasm. If 3 the plant was not supplied 

 with potassium, it grew very little, and very little starch was 

 formed in the chlorophyll corpuscles of the leaves. On the addi- 

 tion of potassium chloride, the starch grains became more nu- 

 merous in the leaves, and made their appearance in other parts 

 of the plants. Potassium, doubtless, plays an important role 

 in the formation and the storing up of carbohydrates, for the 

 organs in which these processes are active, as the leaves, seeds, 

 and tubers, are found to be the richest in this element. 



It has been observed that caesium 4 and rubidium can replace 

 potassium in the food of certain fungi (mould, yeast, and bac- 

 teria). 



Salm-Horstmar describes 5 some experiments, from which 

 he infers that minute traces of lithium and fluorine are indis- 

 pensable to the fruiting of barley. The same investigator has 

 concluded that a trace of titanic acid is a necessary ingredient 

 of plants. 



How Crops Grow, by S. W. Johnson, London, p. 145. 

 Nobbe, Siegert, Wolff, Stohmann, Sachs, and others. 

 Nobbe, Die organische Leistung des Kaliums, 1871. 

 Naegeli, Sitzber. d. Akad. d. Wiss. zu Munchen, 1880. 

 Jour, jur Prakt. Chem., 1884, p. 140. 



