354 



Improvement of Mangels. 



[sept., 



of swedes, mangels, and turnips. These were sown on plots 

 side by side, and treated similarly in every possible way, both 

 culturally and manurially. In the autumn the crop of each 

 plot was weighed, sampled, and analysed. 



From a comparison of the results information was obtained 

 as to the variation among the different strains on different soils 

 and as to the effect of season and manuring, as well as the 

 variation with size and individuality. 



One point which soon became evident was the occurrence of 

 very considerable variation in the chemical composition of 

 individual roots of the same strain, even when grown side by 

 side in the same field, so that in order to obtain a mixed 

 sample representing the composition of the crop it was found 

 necessary to take an average of fifty roots. The variation that 

 occurs is shown by the fact that in 1902 in 200 individual roots 

 of Sutton's Golden Globe four roots were found containing less 

 than 11 per cent, of dry matter, and four roots containing over 

 18 per cent. Similar results were also obtained in the same year 

 with Webb's Golden King and with Carter's 1901, and Messrs. 

 Wood and Berry point out that a plant which varies to this extent 

 ought to be capable of rapid improvement by careful selection. 



Such an improvement, it is well known, has been brought 

 about in the case of the sugar-beet. About fifty years ago 

 Ventzke suggested that sugar-beet workers were selecting fur 

 shape and other external characters, and neglecting the really 

 important point, namely, the sugar : content. Very soon after- 

 wards Vilmorin commenced selecting sugar-beet for compo- 

 sition, his first method being to pick out for seed-mothers roots 

 of high specific gravity. This method he soon changed, and 

 began to select for high specific gravity of juice. In 1867 

 Marck suggested that in selecting there should be an actual 

 determination of the percentage of sugar in the juice by means 

 of the polarimeter, and that, in order to increase the sugar 

 without increasing the other solids of the juice, which interfere 

 with the crystallisation of the sugar, the percentage of total 

 solids in the juice should also be determined, and the sugar 

 calculated as percentage of the total solids, or quotient of purity 

 as it is called. The actual selection is then made for high per- 

 centage of sugar combined with high quotient of purity. 



