Inorganic Constituents of Lichens. 41 



which had never been in contact with rock, after washing as 

 in the previous instances, yielded by incineration 0'4;7 grain 

 of a skeleton answering to the form of the hchen, and consist- 

 ing of silica, iron, phosphates, &c. 



I am thus particular in describing these experiments, made 

 upon a small scale, because I found it extremely difficult when 

 employing a larger amount to separate the extraneous parti- 

 cles which are always attached in considerable quantities to 

 lichens inhabiting the surfaces of rocks. These three experi- 

 ments give a per-centage of ashes amounting to 

 I. II. III. 



6-8 6-75 6*71 



Another specimen, consisting of the upper parts of fronds, 

 afforded only 5 per cent, of ash, in which phosphate of alu- 

 mina constituted a prominent ingredient. The ash in all these 

 examples possessed the form of the lichen, as if the inorganic 

 matter formed the skeleton upon which the organic portion 

 was fixed. It sometimes effervesced slightly on the addition 

 of an acid, and in one instance the carbonate of lime reached 

 a considerable per-centage. On digesting the ash in water, 

 some portion was dissolved ; this solution, on the addition of 

 chloride of barium, gave a white precipitate, part of which was 

 insoluble in nitric acid. On throwing the sulphate of barytes 

 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 

 precipitate partially insoluble in nitric acid. The soluble salts, 

 therefore, appear to be sulphate and phosphate of soda and 

 common salt. The portion of the residue insoluble in water 

 became nearly white when boiled with dilute muriatic acid, 

 and left a gritty powder, which proved to be silica. The mu- 

 riatic acid solution gave a copious precipitate with caustic am- 

 monia; this precipitate was partly soluble in caustic soda, and 

 consisted of peroxide of iron and phosphates of iron, lime and 

 alumina. The results of the analysis of two specimens were 



as follows : — 



I. II. 



Silica 68-4G 64*62 



Soluble salts, consisting of sulphate, phos- 

 phate and muriate of soda .... 0'75 



Alumina and phosphate of alumina . . 0*83 



Peroxide of iron and phosphates of iron 



and lime 22-04 34-55 



Carbonate of lime 8-75 



100- 100- 



