196 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



4. A deposit of wax on the surface diminishes the light passing 

 by 0*9 per cent. 



5. The red colouring matter anthocyan diminished the amount of 

 light passing through leaves of Cornus sanguinea. In ordinary green 

 leaves this was 0 0004, and in the red anthocyan leaf only 0-0001. Young 

 leaves are generally more transparent than the mature form, but this is 

 not always the case, e.g. a young leaf of Coltsfoot only allowed O'OOOT, 

 whilst the mature leaf permitted 0*009 of the light to pass through. The 

 method is fully detailed and is no doubt satisfactory, but some of the 

 results in the tables given on page 65 are very unexpected. — G. F. S.-E. 



Manuring Potatos. 



Potatos, Recent Experiments on the Manuring- of. By R. 



Patrick Wright (Jour. Bd. Agri. vol. vii. No. 4, pp. 438-454 ; March 

 1901). — An important paper giving the results of a considerable number 

 of experiments in the manuring of Potatos which were carried out at the 

 collegiate centres of agricultural instruction in Cheshire, Y^orkshire, 

 Northumberland, and Durham, and in the centre and south-west of 

 Scotland. The experiments were designed with a view to discover the 

 most efficacious and most economical methods of manuring Potato crops. 

 Preference is given to farmyard manure, and data are given showing its 

 value and reliability. Details are also given of experiments with the 

 combination of artificial and farmyard manure, the results being given 

 in tabular form. In summarising the experiments, the author says 

 {I.e. p. 449) : " There is a very distinct indication in all the results that 

 when farmyard manure is applied to the crop in a quantity as large 

 as 15 tons per acre, artificial manures must be carefully selected and 

 used with skill if their employment is to prove profitable, and that 

 even when so employed the amount of profit per acre to be got 

 from their use is not likely to be great. At any rate the addition to 

 15 tons of farmyard manure of the quantities of artificial manures 

 employed in these experiments seem to have brought the total 

 manurial application as closely as possible to the maximum profit 

 point." 



Incidentally other valuable information has been obtained on other 

 points of practical importance. " One is the extent to which the 

 effect of any manures applied to the crop is controlled by the inherent 

 productive capacity of the particular variety of Potato grown. This 

 was very well illustrated in the Cheshire experiments of 1899, where 

 manures were applied to the two varieties, British Queen and 

 Hough Giant. The application of farmyard manure, at the rate of 

 15 tons per acre, produced an increase in the yield of the British 

 ■Queen of 9 tons 18^ cwt. Potatos, while in the Hough Giant the 

 same manure gave an increase of only 7 tons 10 cwt. On two 

 other plots a small dressing only was applied of a complete artificial 

 manure, which produced an increase of yield in the British Queen 

 of 7 tons 1 cwt. per acre ; but only 3 tons 1\ cwt. in the Hough 

 Giant Potato. Both results indicated a capacity in the British Queen 



