256 WATER-CULTURE. 



was offered in large amount; nevertheless, Gorup-Besanez * 

 could detect none in peas and buckwheat cultivated in a soil 

 containing a fair amount of zinc carbonate. It is sometimes 

 said that Viola tricolor and Silene inflata grown on zinc soil take 

 up an appreciable amount of this element ; and further, that 

 certain plants are directly affected in shape b}* the presence of 

 zinc in the soil ; in fact, varieties based upon this supposed 

 relation have been described. The experiments of Hoffmann, 2 

 however, throw much doubt upon the relation of the zinc to a 

 change of form, except in the single case of Viola lutea. 



Aluminium 3 occurs in traces in many plants, while in species of 

 Lycopodium (e. g. complanatum) it is present in large amount. 



Manganese 4 is abundant in the ash of Trapa natans, Quercns 

 Robur, and Castanea vesca. 



Caesium and Rubidium 5 have been detected by the spectro- 

 scope in minute amounts in many plants. 



Fluorine 6 has been found in the ash of Lycopodium clava- 

 tum, and traces of it in other plants. Iodine and Bromine 7 are 

 found in marine algse, in much smaller proportions in aquatics 

 growing in estuaries (for example, Zostera), and in minute 

 amount in some plants grown far from the sea. 



Barium, Strontium, and Silver have been found in the ash of 

 Fucus. Mercury, Lead, Copper, Cobalt, Nickel, Tin, Thallium, 

 Selenium, Titanium, and Boron have all been found by analysts 

 in the ash of certain plants, but alwa3'S in the merest traces. 

 Arsenic 8 has also been detected in a few instances. 



1 Annalen der Chemie und Pharmacie, cxxvii., 1863, p. 243. This paper 

 contains an account of the relations of agricultural plants to metallic poisons. 



2 Botanische Zeitung, 1875, p. 628. 



3 Knop: Lehrbuch, p. 263; Rochleder: Phytochemie, 1854, p. 237. 



4 Wolff's Die Mittlere Zusammensetzung der Asche. 



5 Laspeyres : Annalen der Chernie und Pharmacie, cxxxviii., 1866, p. 126. 



6 Salm-Horstnmr : Annalen der Physik und Chemie, cxi., 1860, p. 339. 



7 Chatin, in Comptes Rendus, Ixxxii., 1876, p. 128. 



8 Numerous references to the literature of this subject will lie found in 

 Sachs's Experimental-physiologic, and in Mayer's Lehrbuch der Agrikultur- 

 chemie. 



