COMPOSITION OF SOiME INDIGEXOUS GRASSES. 219 



set. In order to minimise variations due to weather conditions, 

 samples were collected on bright, sunny days, but not during 

 any period of i^rolonged dry weather. In succeeding years 

 samples were taken from approximate!}^ the same locality as in 

 the case of the first sample. Thus the majority of grasses are 

 represented by three analyses, or two only in the case of the eai'ly 

 flowering species. 



During the year 1921-1922 the scope of the work was enlarged 

 and samples of certain species were collected at monthly 

 intervals, as far as possible at the same stage of growth, so as 

 to study the seasonal variations of the same species. 



Methods of Analysis. 



The official methods as used in the Dei^artment of Agricul- 

 ture for the analysis of feeding stuffs were employed in this 

 investigation, with the addition that true proteins were also 

 determined. " Crude protein " is arrived at simply by taking 

 the figures for total nitrogen and multiplying by 6-25, assuming 

 that all proteins contain 16 per cent, of nitrogen. In grasses and 

 similar immature herbage all the nitrogen is not present as 

 protem, but a variable proportion is accounted for by ammonium 

 compounds and amides, which contain varying amounts of 

 nitrogen, and whose feeding value differs greatly from that of 

 jDrotein. For the determination of true protein the method of 

 Barnstein^ was employed. Briefly, this method is as follows: 

 2 grammes of the sample are boiled with 50 c.c. of water, 25 c.c 

 of copper sulphate solution (60g. per litre) added, and then 25 c.c. 

 of a 1'25 per cent, solution of sodium hydrate, with con- 

 stant stirring. After settling, the supernatant fluid is decanted 

 through a filter and the residue washed by decantation, and 

 finally on the filter. The nitrogen content of the residue is deter- 

 mined as usual, multiplied by 6"25, and taken as true protein. 

 This is, of course, a conventional method, but it gives results 

 that are comparable, especially when dealing with a similar class 

 of feeding stuff, and enables a better estimate of the feeding 

 vakie to be made than if crude pi'otein alone were considered. 



The difference between the total nitrogen and that found by 

 Barnstein's method is the non-protein nitrogen, and as most of 

 it is present as amides it is usually sO' expressed in the results 

 of analysis. Asparagin being taken as a typical commonly 

 occumng amide, the non-protein nitrogen is calculated to this 

 compound by multiplying by 33 



Y. 



The term " amide " is unfortunate, as it covers so great a 

 diversity of compounds, but it has been established by custom. 

 Armsby^ suggests tlie use of the term " non-protein " as being 

 I^referable. 



The nutritive ratio is calculated from the following formula: 



Crude fat x 2-3 + soluble carbohydrates -f- amides x O'o. 



