PROCEEDINGS OF SECTION K. 669 



The ash of the fruit shell of TrajJa natans, according to Molisch 

 (Bied. Cent. 22, 336-338) contains 68 per cent, of FcoOs. 



These are specific instances where Mn, Al, Fe may be considered 

 essential constituents of these plants. 



However, the greatest number of the experiments carried out 

 with these particular elements shows an opposite phenomenon. 

 The quantity of these elements required by plants seems to be very 

 small ; in fact, in nearly all cases dilute solutions gave good results, 

 while greater quantities were distinctly injurious. Herein lies per- 

 haps, the explanation of the different results obtained by many ex- 

 perimenters. 



Let us, in effect, ask the question : What quantity of these rare 

 elements is required by different plants ? 



The usual way of estimating the quantity of manurial elements 

 required by a certain crop is to calculate from the analysis the 

 quantity of such constituent present in the average crop per acre. 

 In other words, knowing that so many cwts. of wheat take away 

 from the soil so many pounds of potash, so many of nitrogen, so 

 many of phosphoric acid, we recommend the application to the soil 

 of a corresponding quantity of these elements, under the form of 

 superphosphate, sulphate of potash, nitrate of soda, &c. 



Applying the same process to those of the catalytic elements, 

 which were estimated in different vegetables, we shall know with 

 some amount of probability the amount necessary to a crop over 

 a certain area. 



Manganese has been found present in many wines, and by many 

 it is said to be always present in wine. The quantity found as 

 Mn. varies between 1 to 3 milligrams per litre of wine.^ On the 

 probable supposition that a corresponding amount is present in 

 the leaves, stems, and other parts of the vines, and admitting an 

 average of 2.5 milligrams for every kilo of crop, and a crop per acre 

 of 10 tons, it follows that a crop of grape vine takes away from the 

 soil manganese to the extent of about 25 grammes per acre. 



Boron has also been found by Henri Hay (Compf. Rend., 1895, 

 896-899), and estimated in wines. It seems to be a constant 

 element of the grape vine. It has been found in the leaves, in the 

 stems, &c. The ash of wine contains an average of 25 milligrams 

 of HgBOg per litre. It follows that 250 grammes of boric acid 

 are taken from the soil by a crop of 10 tons per acre. 



Henri Hay found also that onions contain boron to the extent 

 of 2.1 to 4.6 grammes per kilo of ash. The average crop per acre 

 is 6 to 8 tons. Admitting that onions contain roughly 2 per cent, 

 of ash, in a crop of 8 tons, the quantity of boron taken from the 

 soil varies between 300 and 900 grammes per acre. 



1. Agricultural Gazette of New South Wales, 19, 140. 



