FUNCTION.] OF TISSUE. 169 



With reference to the discrepancy between the first and 

 last of these tables, Payen remarks, that, as alkalies do not 

 remove all the matter of lignification, it is possible that this 

 substance may consist of two kinds of matter, one of which 

 only is capable of being acted upon by azotic acid. He also 

 adds that, although concentrated sulphuric acid has the same 

 power as nitric acid of separating from the primitive tissue of 

 plants their sedimentary matter, yet it possesses this difference, 

 that it gives it the property of becoming blue when acted 

 upon by iodine ; a circumstance which has doubtless given 

 rise to the statement that lignine may be transformed into 

 starch. (Comptes rendus, vii. 1055. 1125.) 



M. Payen, in a second memoir upon this subject, names the 

 unchanged primitive tissue of plants cellulose, and says it has 

 the same composition as starch ; the matter of lignification 

 he regards as the true lignine of chemists. (Comptes 

 rendus, viii. 52.) His analyses of cellulose lie between 43 and 

 45 of carbon in 100; 6-04 and 6'32 hydrogen; and 48'55 

 and 50*59 oxygen, which may be represented by the formulae 

 C 94 H 18 9 + H a O,orC 94 H ao 10 . Leaves cleaned of 

 a waxy incrusting substance, yielded cellular matter of the 

 same composition. Spiral vessels of the Musa merely cleaned of 

 their incrusting substance, by ammonia, water, weak muriatic 

 acid, &c., yielded 0*484 carbon; but on being treated with 

 heated potash, only -44 carbon. Uncontaminated membrane 

 from the grain of wheat had the same constitution as other 

 plants. The cells in the circumference of the grain exhibited a 

 grey colour, which was caused by a gelatinous substance that 

 covers their membrane. The application of tannin coloured 

 and contracted this substance, ammonia and acetic acid 

 dissolved it, and left the pure membrane behind ; a solution 

 of iodine coloured the gelatinous substance yellow, the starch 

 dark violet, and left the simple membrane uncoloured. 

 Vegetable remains, from cow-dung, after having been digested, 

 had the before-mentioned composition. The hair of the seed 

 of the Virginian Poplar Tree behaved in the same manner as 

 cotton. It was difficult to separate firwood from all foreign sub- 

 stances ; the cellulose, however, after this was accomplished, 



