184 



Nutritive Matter of Grasses. 



introduced into a drjing-oven, the temperature of which would 

 vary between 120^ and 160° Fahr., and in which they remained 

 for two or three weeks. A portion of each sample was in each 

 case dried in a water-bath, but it was found that at a tempera- 

 ture of 212° further diminution of weight seldom occurred. 



The samples were then broken up into fine powder and passed 

 through a sieve of forty holes to the inch (every part of the grass 

 being of course made to pass through the sieve), and preserved 

 for analysis. 



2. For the determination of albuminous matter, a portion of 

 the grass dried anew in the water-bath was burned with soda- 

 lime in the usual way, the nitrogen being weighed as platinum 

 salt. The quantity of albuminous matter was calculated from 

 the nitrogen upon the datum that 15'75 per cent, of this element 

 represents 100 parts of the different albuminous constituents — this 

 being the average percentage of nitrogen in these constituents. 



I am quite aware that an objection has been raised against 

 this method of determining albuminous matter, and one that 

 deserves some consideration. Dr. Voelcker, I believe, first 

 pointed out that the juices of vegetables contained ammoniacal 

 salts, which in this method of analysis would tend to increase 

 the quantity of nitrogen, and therefore to exaggerate the pro- 

 portion of albuminous matter as calculated from it. In the first 

 place I should state that the analyses now given were made 

 before this question was opened ; consequently, however much 

 weight I might be disposed to attach to the objections, I am not 

 in a position to modify my methods in accordance with it. In 

 the second it does not appear to me to be of any great import- 

 ance in the present instance. 



Dr. Voelcker states (Report of the British Association for 

 1850 — Transactions of the Sections, p. 64), that in fungi (or 

 Agarics) examined by him, one-third of the nitrogen present 

 existed in the state of ammoniacal salts. Probably, of all the 

 vegetables he could have selected, none would have been so 

 likely to give this result as the one in question, from the rapidity 

 of its growth, and from the fact that this growth takes place in 

 great part when the chief agents of elaboration — light and heat 

 — are withdrawn. But, without denying the importance of 

 Dr. Voelcker's observations on this subject, which were not con- 

 fined to the mushroom, I am induced to believe that such a cause 

 of error could not materially affect the analyses which are now 

 published, and those very numerous results of other chemists 

 which have been conducted on the same principle. If ammoni- 

 acal salts in the plant are supposed to cause a serious error in 

 the estimation of nitrogen, that error must be common to all the 

 samples of grasses examined in a degree only influenced by the 



