Dr. R. D. Thomson on Parietm, a Yellow Colouring Matter, 185 



from all extraneous substances, yielded 6 per cent, of ashes, consisting 

 of similar ingredients. Hence it would appear, that tliis species of 

 plants contain no inconsiderable amount of substances calculated to 

 serve as vegetable manure. The ash possessed the form of the lichen, 

 and a slight iron tint; it eflforvesced slightly on the addition of an 

 acid. In one instance, some carbonate of lime was present. On 

 digesting the ash in water, a minute portion was dissolved. This 

 solution, on the addition of chloride of barium, gave a white pre- 

 cipitate, part of which was insoluble in nitric acid. On throwing the 

 sulphate of barytos on a filter, and adding caustic ammonia to the 

 filtered liquid, a flocky precipitate — phosphate of barytes—felL The 

 addition of an alcoholic solution of bichloride of platinum, gave no in- 

 dication of the presence of potash. Nitrate of silver gave a flocky 

 precipitate, insoluble in nitric acid. The soluble salts, therefore, 

 appear to be sulphate and phosphate of soda and common salt. Tho 

 portion of the residue insoluble in water, became nearly white when 

 boiled with dilute muriatic acid, and left a gritty powder, which, 

 affording a nearly colourless glass with carbonate of soda before the 

 blowpipe, was obviously siHca, with slight impurity. The muriatic 

 acid solution gave a copious reddish precipitate, with caustic ammonia. 

 This precipitate was partly soluble in caustic soda, and consisted 

 of phosphates of iron, alumina, and lime. The latter precipitates 

 being tested with lead, yielded a precipitate of phosphate of lead, 

 soluble in nitric acid. The results of the analysis of two specimens 

 of ashes were as follows; — 



Silica, 



Soluble salts, sulphate, phosphate, and 



muriate of soda, .... 

 Peroxide of iron, and phosphates of iron 



and lime, 



Phosphate of alumina, .... 

 Carbonate of lime, .... 



100- 100-00* 



From these facts it is evident that this lichen requires the same 

 inorganic constituents for food as other plants, with this difference, 

 that the amount of inorganic substances present in its composition is 

 greater than in higher orders of plants, but in a proportion tenduig 

 towards that existing in the sea weeds ; another character, therefore, 

 in addition to the general external features, indicating an alliance be- 

 tween the algto and lichens. 



* Mr. David Murdoch assisted mo in the first analysis, and Mr. James Murdoch in 

 tho second. 



