172 QUARTERLY JOURNAL. 



plants over and above that contained in the seeds sown, M. Wieg- 

 mann sowed seeds of cresses in fine platinum wire, in a platinum 

 crucible, and watered them with distilled water. They grew well, 

 but the ashes of the cresses contained only the same weiglit of in- 

 organic matter as the seed which had produced them, a result which 

 it will be seen, differed from that of plants growing in the sand, 

 which contained at least twice as much inorganic matter as the seed 

 from which they were grown. The sand used in this experiment 

 was not pure silex or quartz, but a soil probably derived from 

 granite, but from which not only all the vegetable matter had been 

 removed by ignition, but all the free lime and alkalies by acid and 

 full washing afterwards by water. 



The results of these experiments go to prove, 



1st. That inorganic matter is essential to the perfect plant, as no 

 fruit was produced w^here it was totally wanting or even deficient 

 in quantity. 



2d. That plants by their roots possess the power of decompos- 

 ing the compound of inorganic matter, as in the experiment with 

 the sand from which all the free soluble matter had been removed 

 as stated above, 



3d. That the opinion which has been advanced by some physio- 

 logists that the elements may be formed in plants, is incorrect, as is 

 shown by their absence in the cresses w'hich grow in the platinum 

 wire. 



It is supposed, however, that all the inorganic matter is not ne- 

 cessary to the perfection of the plant, but that some elements may 

 be substituted for others, as soda for potash, magnesia for lime,&c. 



