14 BARER ELEMENTS 



as a plant food, but is often found in the ashes of plants, notably in 

 those of tea and of Paraguay tea or Mate. 



Investigations carried out at Woburn l and at Tokyo, in Japan, 

 show that manganese compounds applied in small quantity to soil 

 produce a distinctly stimulating effect upon many plants, especially 

 leguminous ones. Increases of 50 per cent in the straw and 25 per 

 cent in the grain were produced with peas by the addition of -015 per 

 cent of manganous sulphate to the soil. 



Confirmation of this effect has been furnished by Bertrand 2 with 

 oats, and by Sutherst, in Natal (private communication), with maize, 

 while Nagaoko records an increase of 15 per cent in a crop of rice 

 when using manganese sulphate at the rate of 100 kilos per 

 hectare. An increased quantity of manganese was found in the ash of 

 plants grown in soil to which manganese salts had been added. 



The author is of opinion that the action of the manganese is to be 

 regarded rather as medicinal than as a food, and that it acts as a 

 " tonic " much in the same way as ferrous sulphate is usually believed 

 to do. It is thought that it plays some part in aiding the action of 

 the oxydases in the leaf. 



It would seem that from 50 to 100 kilos per hectare ( = 44-6 to 

 89*2 Ib. per acre) is the maximum dressing to be used and that larger 

 quantities act injuriously upon the crop. Salomone 3 states that 

 manganic compounds are more toxic than manganous salts. 



Titanium, which resembles silicon in its chemical functions, is 

 not nearly so abundant. Its presence in the plant is usually over- 

 looked, though, according to Wait, 4 it is almost invariably present in 

 plant ash. 



Zinc has been found in the ashes of plants growing in localities 

 where zinc ores blende, ZnS, or calamine, ZnC0 3 occur. 5 A plant, 

 Viola calaminaria, grows in certain parts of Germany and its 

 presence is regarded as indicative of the presence of zinc deposits in 

 the neighbourhood where it is found (Liebig). The element, however, 

 rarely occurs in animal or plant tissues, though its presence in certain 

 food stuffs, e.g., dried fruits through contamination from zinc utensils 

 is not uncommon. 



Lithium has been found in the ashes of many plants, notably in 

 those of tobacco leaves; it does not appear to have any important 

 functions, but rather to be an accidental constituent. 



Copper appears to be an essential constituent of certain gaily 

 coloured feathers of tropical birds and has been occasionally found in 



1 Jour. Roy. Agric. Soe., 1903, 64, 348; 1904, 65, 306; 1905, 66, 206. 

 2 Cornptes Rendus, 1905, 141, 1255. 

 3 Chem. Zentr., 1906, ii. 532. 



4 Jour. Soc. Chem. Ind., 1889, 367. 



5 Fricke, Cheni. Zentr., 1900, ii. 769 : also Labard, Zeit. Nahr. Genussm. , 

 1901, 4, 489. 



