256 WATER-CULTUKE. 



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 talie 

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

 certain plants are directl}' affected in shape bj' the presence of 

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

 relation have been described. The experiments of Hoffmann, ■■* 

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

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



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

 Lyeopodiura (e. g, coniplanatum) it is present in large amount. 



Manganese ■* is abundant in the ash of Trapa natans, Quercus 

 Robur, and Castanea vesca. 



CiJesium and Rubidium ^ have been detected by tlie spectro- 

 scope in minute amounts in many plants. 



Fluorine" has been found in the ash of L}'copodinm clava- 

 tnm, and traces of it in other plants. Iodine and Bromine ' are 

 found in marine algae, 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 In' analysts 

 in the ash of certain plants, but always in the merest traces. 

 Arsenic^ has also been detected in a few instances. 



1 Annalen der Chemie untl Phannaoie, cxxvii., 1863, p. 243. This yiaper 

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



2 Botanische Zeitung, 1875, p. 628. 



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

 * Wolff's Die Mittlere Zusammensetzung der Asche. 



^ Laspeyres : Annalen der Chemie und Pharaiacie, cxxxviii., 1866, p. 126. 



^ Salm-Horstmar : Annalen der Physik und Chemie, cxi., 1860, p. 339. 



' Chatin, in Comptes Eendus, Ixxxii., 1876, p. 128. 



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

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

 chemie. 



