THE DISTRIBUTION OF DRY MATTER AND NITRO- 

 GEN IN THE POTATO TUBER. VARIETY, KING 

 EDWARD. 



By MARY D. GLYNNE, B.Sc. 



AND 



VIOLET G. JACKSON, B.Sc. 

 [Rolhamsled Experiment Station.) 



The following investigations arose out of certain work undertaken at 

 the Rothamsted Experiment Station in 1918 in connection with the 

 Food Production Department. This involved sampling a large number 

 of tubers. Investigations into the best method of sampling suggested 

 the advisability of studying in detail the distribution of dry matter and 

 nitrogen in the different parts of the tuber. 



PREVIOUS INVESTIGATIONS. 



As early as 1892 M. Douillet{i) discussed the uneven distribution of 

 starch in the different parts of the tuber. He showed that chemical 

 analysis and microscopical examination reveal the fact that starch is 

 much more abundant near the periphery than in the inner part of the 

 potato, and that the grains appear to be formed in the neighbourhood of 

 the vascular system. He also showed that the two ends of the tuber 

 vary in starch content but not always in the same direction. At the 

 time of lifting the starch content is higher towards the point of 

 attachment than towards the sprout end, but the reverse is true when 

 the buds are sprouting. 



M. Douillet used the coring method for sampling, but this was later 

 criticised by Coudon and Bussard who point out the difficulty of 

 directing a core exactly along an axis. Slight deviation from the axis 

 might cause serious error. 



Doerstling(2) in 1895 arrived, by a completely different method, at 

 conclusions which agree in the main with those of later workers. He 

 took a core along one of the axes of the tuber, divided it into discs 2 mm. 

 thick and determined the specific gravity of each disc. He argued from 



Journ. ol Agric. Sci, ix 10 



