3m 



On the Composition of the 



CojnposUion of tha Ash of Pa7'snips. 



Potash . . ^. . 36:12 



Soda ..... 3-1] 



Magnesia . . . . 9-94 



Lime . . . . . 1143 



Phosphoric acid .... 18-66 



Sulphuric acid .... 6-50 



Silica . . . . . 4-10 



Phosphate of iron . . . 3-71 



Chloride of sodium . . . 5'54 



Bj moistening a transverse section of the root of parsnip with 

 tincture of iodine the external layers are coloured deep violet- 

 blue, whilst the remaining portion of the root is not discoloured. 

 Bj this means three distinct circles can be distinguished on a 

 transverse section of parsnip : one interior, formed by the heart 

 of the root, an exterior coloured deep violet-blue by the pro- 

 duction of iodide of starch, and an intermediate circle between 

 the heart and the exterior blue coloured zone. This shows dis- 

 tinctly that starch does not exist in the heart, nor in the layers 

 next to it, but that it is all deposited in the external layers of 

 the root. 



On further examination of these three sections of the root, I 

 have also found that the intermediate layers contain much more 

 protein compounds than either the heart or the outer layers, where 

 the starch is deposited. The intermediate portions between the 

 heart and the outer layers, indeed, contained in this instance 

 one-half more of flesh-forming constituents than the other por- 

 tions of the roots, as will be seen from the following determina- 

 tions : — 



Layers between 

 In outer Layers. Heart, the Heart and the 

 outer Layers. 



Percentage of nitrogen . . 1-039 r067 1-500 

 equal to • 



Protein compounds . . . 6-493 6-668 9-375 



It is worthy of notice, that the albuminous or protein com- 

 pounds are not uniformly distributed throughout the whole mass 

 of the root. I have not examined any other root in this respect ; 

 but, judging from analogy, we may expect to fmd a similar dis- 

 tribution in other kinds of roots. 



In ascertaining the nutritive value of roots, which is now 

 usually done by the indirect method of combustion, care must be 

 taken to obtain for analysis a fair average sample of the whole 

 root, for the nutritive value of the root will either be stated too 

 high or too low if the portions analysed contain more of the 

 exterior or the intermediate portions of the root, as actually 

 contained in the whole root. For this reason I find it advisable; 

 to prepare the sample of the root to be used for combustion, by 



