4-26 The Rev. J. B. Reade on the Chemical Composition 



lular tissue that it might be represented by the engraving in 

 your own work, Plate II. fig. 9. 



With membrane and fibre isolated to this extent, Mr. Rigg 

 commenced his experiments; and 1 believe that I am not in 

 error when I state that the ultimate analysis of these textures 

 was thus for the first time attempted. There is no record of 

 similar experiments, for, as Professor Henslow justly ob- 

 serves *, " all that is known of the composition of these tex- 

 tures has been derived from experiments made upon the gross 

 material, which is found to be composed of the three ele- 

 ments, oxygen, hydrogen and carbon ;" a result which clearly 

 shows that the gross material referred to consisted of both the 

 elementary organs, viz. cells and tubes, as they conjointly en- 

 ter into vegetable structure. 



But even allowing Professor Henslow's objection its full 

 force, and granting that " fibre externally lined the cells of 

 the cellular tissue" analysed by Mr. Rigg; and also that 

 " the spiral vessels contained both membrane and fibre ;" then, 

 bearing in mind that "it has not hitherto been ascertained 

 whether the membrane and fibre which compose the cells 

 and tubes in different parts of plants are always of the same 

 kindf", I would offer the result of the analysis as a proof 

 that the membrane and fibre which compose the cells are 

 essentially different, in a chemical point of view, from the 

 membrane and fibre which compose the spiral vessels; the 

 former invariably containing an excess of oxygen, and the 

 latter an excess of hydrogen. And thus we appear to arrive 

 at the chemical composition of the elementary tissues, and that 

 too in such a way as to be an important approximation to 

 the composition of the elementary textures ; for it cannot 

 be doubted that membrane predominates over fibre in the 

 cells, and that fibre predominates over membrane in the spiral 

 vessels. 



I learn, from the report in " the Athenaeum," that you 

 commenced your own observations by stating, that " it is im- 

 portant that facts of this kind should be well made out ;" a 

 remark which encourages me in the hope that you will fa- 

 vourably receive my present attempt to substantiate the re- 

 sults or my friend's experiments. But you go on to charge 

 me with the fault, condemned by a great authority : 



" Aut operae nimium celeris curaque carentis, 

 Aut ignorata3...artis." 



For you proceed, " As a proof of want of care in the paper, 



• Principles of Botany, p. 13. 1 Ibid. 



