THE VOLATILE PART OF PLANTS. 113 



Vines, who lias examined the aleurone of many plants, 

 finds it in all cases more or less soluble in water. The 

 globulin doubtless goes into solution by help of the salts 

 present. Vines also states that a body soluble in water, 

 having the properties of a proteose (Jiemialbumose), is 

 universally present in aleurone. 



Estimation of the Albuminoids. — The quantitative sep- 

 aration of these bodies, as they occur in plajats, is mostly 

 impossible in the present state of science. In many cases 

 their collective quantity in an organic substance may be 

 calculated with approximate accuracy from its content of 

 nitrogen. 



In calculating the nutritive value of a cattle-food the 

 . albuminoids are currently reckoned as equal to its nitro- 

 gen multiplied by 6.25. This factor is the quotient ob- 

 tained by dividing 100 by 16, which, some 35 years ago, 

 when cattle-feeding science began to assume its present 

 form, there was good reason to assume was the average 

 per cent of nitrogen in the albuminoids. As Ritthausen 

 has insisted, this factor is too small, since the albuminoids 

 of the cereals and, of most leguminous seeds, as well as of 

 the various oil-cakes, contain nearer 17 than 16 per cent 

 of nitrogen, if our analyses rightly represent their com- 

 position, and the factor 6 (= 100 -j- 16.66) would be 

 more nearly correct. 



This mode of calculation only applies with strictness 

 where all the nitrogen exists in albuminoid form. This 

 appears to be substantially true in most seeds, but in case 

 of young grass and roots there is usually a considerable 

 proportion of non-albuminoid nitrogen, for which due 

 allowance must be made. (See Amides.) * 



*Am,m,onia, NHj, and Nitric acid, NHO3. These bodies are mineral, not 

 organic substances, and are not, on the whole, considerable ingredients 

 of plants. They are however the principal sources of the nitrogen of 

 vegetation, and, serving as plant-food, enter plants through their roots, 

 chiefly from the soil, and exist within them in small quantity, and for 

 a time, pending the conversion of their nitrogen into that of the 

 amides and albuminoids, to whose production they are probably 

 essential. In seeds and fruits, and in mature plants, growing in soils 



