Botanical Society of Edinburgh. 229 



ashes were then mixed in the cold with oil of vitriol, so as to secure 

 the decomposition of the salts of volatile acids present. The mixture 

 was then transferred to a retort, or flask, provided with a bent tube 

 dipping into water, and the liquid raised to the boiling-point, when 

 fluorine, if present, was evolved in combination with the silicon of the 

 silica, as the gaseous fluoride of silicon, which dissolved in the water 

 with separation of some gelatinous silica. The resulting solution was 

 neutralized with ammonia and evaporated to complete dryness, when 

 the whole of the silicon passed into the condition of insoluble silica, 

 and water dissolved the fluoride of ammonium. The solution of this 

 fluoride could then be dried up and moistened with sulphuric acid, 

 when hydrofluoric acid was evolved, which might be made perma- 

 nently to record its presence by causing it to etch glass in the usual 

 way. * The author has in the meanwhile applied this process almost 

 solely to the stems and trunks of plants, especially to those containing 

 silica, reserving for subsequent investigation their other organs, espe- 

 cially their seeds and fruits. The following were the results ob- 

 tained : — ol 



Table of Plants examined for Fluorine. The numbers represent 

 grains of ashes, except in the case of Tabasheer and Jf^pod Opal. 

 The blanks imply that the weight was not ^^^^^^^'^ |Ty7 bootet^bni; 

 Ashes in grains. Name of plant. 



200 Equisetum litnosum Distinct etching. 



Bambusa arundinacea Ditto. 



Charcoal (derived chiefly from Oak, 



and to a smaller extent from Birch) Ditto. ,,, 



€oal DittoJ '^^^ 



Barley straw Ditto. 



Hay (Ryegrass) Ditto. 



35 Equisetum variegatum Faint etching. 



19 hyemale Ditto. 



255 palustre .. Ditto. p<-o^4 



Dactylis ccespitosa Ditto. '^ ^^\^ 



99 Elymus arenarius Ditto. 



495 Saccharum officinarum Ditto. 



i040 African Teak Ditto. 



Smilax latifolia No etching. 



Rosmarinus officinalis Ditto. 



^35 Bambusa Nepalensis Ditto. 



^ibih^u , 'Polypodium vulgare Ditto. 



f \"';;'S37 Tree Fern Ditto. 



ii>. -.^24 Thalaris arundinacea Ditto. nHU\ 



''^' ■' ^40 Malacca Cane Ditto. ^ ''- ' 



50 Cocoa-nut shell Ditto. 



127 Tectona grandis Ditto. 



Y"' ■ '80 Tabasheer Ditto. 



' '' 1680 Wood Opal Ditto. 



On this table the author remarked, that the siliceous stems which 

 iie had found to abound most in fluorine, were exactly those which 

 •fiontained most silica. In particular, deep etchings were procured 



