136 D^ ALISON'S OBSERVATIONS ON 



ing the germination of seeds, and in both these cases is useful as giving a 

 greater degree of solubility to the starch Avhence it is formed. In both cases it 

 disappears, and probably is converted into some of the varieties of starch, as the 

 vital actions of the plant become more vigorous. Its composition, in its different 

 varieties, as given by most analysts, C12 Hu On, or Cio Hio Oio, or even C12 Hu Ou, 

 denotes that if it be formed from the starch, C12 IIio Oio, it must be either by the 

 addition of the elements of water, or by the abstraction of carbon ; and as its for- 

 mation, during the germination of seeds, is attended with evolution of carbonic 

 acid, it seems most probable that, in that case at least, it is formed in this last 

 way, under the influence of the oxygen of the air. It appears again in tlie nec- 

 taries of flowers, and in the ripening of fruits, as one of the latest results of the 

 vital action of plants, in those parts of them which are fully exposed to air and 

 light, but at a time when we may reasonably suppose that the vital affinities are 

 becoming comparatively ineffective, and when carbonic acid is again evolved. It 

 may be formed by the chemist from some of the varieties of starch b}"^ a kind of 

 fermentation, excited by diastase, as in malting; or by a catalytic action of 

 sulphuric acid ; and it is formed from starch merely by the agency of cold, as 

 in frozen potatoes, and from inuline merely by continued boiling in water ; so 

 that its formation from starch in vegetables seems to be most jirobably a simjjle 

 chemical change, not the effect of a vital affinity. Farther, it is a compound 

 which takes the crystalline form, essentially different from any form assumed 

 by those parts of organized structures which exhibit truly vital phenomena, 

 and retains its properties when exposed to air and water better than any of the 

 matters of which organized forms are composed. From all these facts it may 

 be inferred, with great probability, that sugar, as it appears in the living vege- 

 table, is generally to be regarded as a first product of decomposition of starch, b}- 

 the agency of water and of the oxygen of the air, which appears to be the 

 great agent in the resolution of those compounds, which the vital affinities have 

 buUt up. 



6. On the other hand, the relation of starch and cellulose to the lignin, 

 which forms the greater part of the solid matters of dicotyledonous plants seems 

 to be nearly the reverse of their relation to sugar. This matter is always found 

 incrusting, or incorporated with, the cells of vegetable textures ; it gives them 

 their solidity and strength, which all decompositions by chemical agents impair ; 

 it cannot be formed from the compounds of starch by artificial means, but is 

 formed from them in greatest quantity when the vital actions of plants are 

 strongest ; and its composition is alwaj's stated as differing from the amylaceous 

 compounds by containing more carbon ; and less oxygen, in proportion to the 

 hydrogen, than exists in the composition of water ; its formula being stated as 

 C'lo II23 O18. This, therefore, would appear to be clearly the result of truly vital 

 affinities, continuing to actuate the elements of starch, after the formation of the 



