in the Stems of Graminece, Equisetacecv, fyc. 357 



537 Tree Fern, No etching. 



24 Phalaris arundinacea, 

 240 Malacca cane, 



50 Cocoa-nutshell, 



127 Indian teak (Tectona grandis), ... 



80 Tabasheer, 



-icon -rar j i 



1680 Wood opal, 



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

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

 contained most silica. In particular, deep etchings were procured 

 from the Equisetacese (horsetails), and from the G-raminese (grasses), 

 especially the common bamboo. The last was known to contain 

 silica in such abundance that it collected within the joints in white 

 masses, nearly pure, and had long, under the name of Tabasheer, 

 been an object of interest to natural philosophers. The horsetails 

 were scarcely less remarkable, for the amount of silica contained in 

 their stems, which had led to the employment of one of them (Dutch 

 rush, Equisetum hyemale), in polishing wood and metals. The 

 African teak, which, like the bamboo, is known sometimes to secrete 

 silica, was also found to contain fluorine, though much less largely 

 than the plants named ; whilst the strongly siliceous stems of barley 

 and ryegrass also yielded the element in marked quantity. The 

 sugar-cane, however, gave less striking results than might have been 

 expected, and the same remark applied to the Malacca cane. Two 

 specimens of silicified wood and one of Tabasheer gave no evidence 

 of the presence of fluorine. So far, however, as the plants named in 

 the preceding Table, are concerned, the author does not wish it to 

 be inferred, from the negative results which are detailed, that the 

 plants in question are totally devoid of fluorine. With larger quan- 

 tities of their ashes, positive results would in all probability be ob- 

 tained. 



The author's general conclusions were as follow : — 1st, That 

 fluorine occurs in a large number of plants ; 2d, That it occurs 

 in marked quantity in the siliceous stems of the Graminece and 

 JEquisetacece ; 3d, That the quantity present is in all cases very 

 small, for although exact quantitative results were not obtained, it 

 is well known that a fraction of a grain of a fluoride will yield, with 

 oil of vitriol, a quantity of hydrofluoric acid sufficient to etch glass 

 deeply, so that the proportion of fluorine present, even in the plant 

 ashes which contain it most abundantly, does not probably amount 

 to more than a fraction per cent, of their weight. The proportion 

 of fluorine appears to be variable, for different specimens of the 

 same plant did not yield concordant results. 



In this, however, there is nothing anomalous, for some Bamboos 

 yield Tabasheer largely, whilst others are found to contain none. 

 It seems not unlikely that soluble fluorides ascending the siliceous 

 stem of a plant, on their way to the seeds or fruits in which they 



