172 On the Secretion of the Leaves and Stems of the Ice-plant. 



which the leaves are covered, with a needle, and collecting the 

 fluid in a glass bottle. The fluid thus obtained was colourless 

 and nearly clear, without smell, and possessing no distinctly 

 pronounced taste. Litmus-paper dipped in it was very slightly 

 turned red, showing the presence of merely traces of a free acid 

 or an acid salt. In order to free it entirely from any particles of 

 epidermis which might accidentally have mingled with the liquid, 

 I filtered it through white filtering-paper. The fluid passing 

 through the filter slowly was now perfectly clear. On heating 

 to 212° F. white flakes were separated, which proved to be iden- 

 tical with vegetable albumen. They were collected in a filter, and 

 the filtrate evaporated to dryness on a water-bath. During the 

 evaporation the liquid turned yellow, particularly when evapo- 

 rated to a small bulk, and left a brownish-coloured, very hygro- 

 scopic residue, which redissolved in a small quantity of distilled 

 water, leaving but a trace of a humus-like, dark-coloured organic 

 substance undissolved. 



The chemical nature of the fluid from which the albumen had 

 been separated, was ascertained as far as possible by the follow- 

 ing tests : — 



Ammonia produced no change. 



Carbonate of ammonia gave no precipitate. 



Carbonate of soda on boiling gave a white precipitate. 



Oxalate of ammonia produced no change. 



Phosphate of soda and ammonia, added to the concentrated 

 liquid, gave a crystalline white precipitate of phosphate of mag- 

 nesia and ammonia. 



Chloride of platinum, added to the concentrated liquid after 

 the removal of the magnesia, produced a crystalline yellow pre- 

 cipitate. 



The presence of soda was indicated by the yellow colour given 

 to the alcohol flame. 



Lime-water produced a white precipitate. 



Sulphate of lime likewise produced a white precipitate. 



Chloride of barium gave a heavy white precipitate. 



Nitrate of silver gave a white flaky precipitate, soluble in am- 

 monia, but insoluble in nitric acid. 



Acetate of lead produced a white precipitate. 



Basic acetate of lead gave a voluminous white precipitate. 



A portion of the water evaporated to dryness and heated to 

 redness left a white ash which effervesced with acids, indicating 

 the presence of carbonates, originated from organic acids present 

 in the fluid. 



The nature of the organic acids, which in all likelihood ac- 

 companied the oxalic acid, I could not determine from want of 

 material. The presence of oxalic acid however is distinctly indi- 



