L 279 3 



Glass Wort (Sa/sola Soda^) when it grows in inland 

 situations, afford the vegetable alkali; when it grows 

 on the sea shore where compounds which afford the 

 fossile or marine alkali are more abundant, it yields 

 that substance. Du Hamel found, that plants which 

 usually grow on the sea shore, made small progress 

 when planted in soils containing little common salt. 

 The sunflower, when growing in lands containing no 

 nitre, does not afford that substance; though when 

 watered by a solution of nitre, it yields nitre abundant- 

 ly. The tables of de Saussure, referred to in the 

 Third Lecture, shew th^t the ashes of plants are simi- 

 lar in constitution to the soils in which they have 

 vegetated. 



De Saussure made plants grow in solutions of 

 different salts, and he ascertained, that in all cases, 

 certain portions of the salts were absorbed by the 

 plant and found unaltered in their organs. 



Even animals do not appear to possess the 

 power of forming the alkaline and earthy substan- 

 ces. Dr. Fordyce found, that when canary birds 

 at the time they were laying eggs were deprived of 

 access to carbonate of lime, their eggs had soft shells; 

 and if -there is, any process for which nature may be 

 conceived most likely to supply resources of this kind, 

 it is that connected with the reproduction of the spe- 

 cies. 



As the evidence on the subject now stands, it 

 seems fair to conclude that the different earths and 

 saline substances found in the organs of plants, are 

 supplied by the soils in which they grow; and in no 



