670 PROCEEDINGS OF SECTION K. 



Iodine was found by Bourget {Compt. Rend., 1899, 129, 

 768-770) in green haricots in the proportion of 0.32 milligrams per 

 kilo, in garlic 0.94 per kilogram. At the rate of 10 tons per acre 

 crop, the quantity of iodine taken by the green haricots would be 

 32 grammes, by garlic 94 grammes. 



Barium has been found by Hornberger in plant and soil. 

 (Kichard Hornberger. Land Vers., 1899, 91, 473-478). The 

 average quantity was 1 per cent, of ash of the trunk wood of two 

 copper beeches. On the basis of 2 per cent, of ash in the wood, 

 and of a growth of the forest equal to 10 tons per acre, it follows 

 that the amount of barium required by such crop is about 2 kilo- 

 grammes per acre. 



Copper was estimated in leaves of plant never treated with 

 copper salts. (See Sestini, Staz. Sper. Agr. Ital., 2^, 115-132). 

 From the quantity found it would appear that a crop of 10 tons 

 requires an average of 55 grammes of copper. 



Working on Policarpea spirostylis E. Heckel {Bull. Soc. Bot. 

 France, 1899, .'^6, 42-43) found copper at the rate of 300 grammes 

 of Cu per a crop of 10 tons. 



Titanium was found by C. E. Wait (J. Am. Chem. Soc, 1896, 

 18, 402-404) in cow pea ash, in cotton seed meal ash, &c. Admit- 

 ting both cow pea and cotton seed meal containing 1.5 per cent, ot 

 ash, it appears that the quantity of titanium eliminated from the 

 soil by a 10-ton crop of these vegetables is of about 30 grammes. 



A. Ost (Ber. 26, 151-154) found small quantities of fluorine in 

 all the plants he examined, at the rate of about 0.01 per cent. On 

 an average of ash of 2 per cent., a 10-ton crop would take 20 

 grammes of fluorine from the soil. 



It follows from these calculations that very little chance of good 

 results was attached to all those experiments, in pots or in the field, 

 where the quantity of these elements supplied to the different 

 plants was very much in excess of what appears to be the real want 

 of the generality of the plants. 



At the rate, and in the form in which some of these rarer 

 elements were added, it need not be matter for surprise if noxious 

 effects were often observed. The fact that good results were ob- 

 tained in many instances with a considerable amount of catlytic 

 manure would show that the amounts found by the analysis do not 

 correspond to the optimum dose that the plant may require. 



However it may be, it is evident that lo enlarge our knowledge 

 of manuring, we have to turn our efforts towards the research and 

 estimation of these rare elements in the ashes of vegetables. We 

 come back to the old idea of Liebig and contemporaries that the 

 analysis of ashes was the basis of rational and scientific manuring. 



