116 OF THE INORGANIC CONSTITUENTS OF PLANTS. 



condition is not permanent, and when the blossoms 

 have again become colorless, none of the coloring 

 matter remains ; and if it should occur that any of 

 its elements were adapted for the purposes of nutri- 

 tion of the plant, then these alone would be retained, 

 whilst the rest would be excreted in an altered form 

 by the roots. 



Exactly the same thing must happen when we 

 sprinkle a plant with a solution of chloride of potas- 

 sium, nitre, or nitrate of strontia ; they will enter 

 into the different parts of the plant, just as the col- 

 ored juice mentioned above, and will be found in 

 its ashes if it should be burnt at this period. Their 

 presence is merely accidental ; but no conclusion can 

 be hence deduced against the necessity of the pres- 

 ence of other bases in plants. The experiments of 

 Macaire-Princep have shown, that plants made to 

 vegetate with their roots in a weak solution of ace- 

 tate of lead, and then in rain-water, yield to the lat- 

 ter all the salt of lead which they had previously ab- 

 sorbed. They return, therefore, to the soil all mat- 

 ters which are unnecessary to their existence. Again, 

 when a plant, freely exposed to the atmosphere, rain, 

 and sunshine, is sprinkled with a solution of nitrate 

 of strontia, the salt is absorbed, but it is again sep- 

 arated by the roots and removed further from them 

 by every shower of rain, which moistens the soil, so 

 that at last not a trace of it is to be found in the 

 plant. 



Let us consider the composition of the ashes of 

 two fir-trees as analyzed by an acute and most accu- 

 rate chemist. One of these grew in Norway, on a 

 soil the constituents of which never changed, but to 

 which soluble salts, and particularly common salt, 

 were conveyed in great quantity by rain-water. How 

 did it happen that its ashes contained no appreciable 

 trace of salt, although we are certain that its roots 

 must have absorbed it after every shower ? 



We can explain the absence of salt in this case by 

 means of the direct and positive observations refer- 



